Friday, February 20, 2026

Geometry Problems of the Day (Geometry Regents, August 2025 Part I)



This exam was adminstered in August 2025.

More Regents problems.

August 2025 Geometry Regents

Part I

Each correct answer will receive 2 credits. No partial credit.


1. An equilateral triangle is continuously rotated around one of its altitudes. The three-dimensional object formed is a

(1) cone
(2) sphere
(3) cylinder
(4) pyramid

Answer: (1) cone


Imagine an equilateral triangle taped to a lollipop stick that running from one corner and through the midpoint of the opposite side. If you were to spin the stick, the stuff that the triangle will pass through will form a cone. That is Choice (1).

It is impossible to get any of the others from a triangle.




2. On the set of axes below, quadrilateral BDGF is rotated 90 degrees clockwise about the origin and then reflected over the y-axis. The image of quadrilateral BDGF is quadrilateral MQSP.

Side BD will always map onto

(1) MP
(2) PS
(3) MQ
(4) SQ

Answer: (3) MQ


Follow the movement. When BDGF is rotated 90 degree clockwise, the image appears in Quadrant IV with BD on top, closest to the x-axis. When this image is reflected across the y-axix, B'D' maps onto MQ, which is Choice (3).




3. In right triangle JOE, hypotenuse JO = 31.8 and m∠J = 38°. To the nearest tenth, the length of EJ is

(1) 19.6
(2) 25.1
(3) 40.4
(4) 51.7

Answer: (2) 25.1


Angle E is the right angle. EJ is adjacent to angle J, and you're given the hypotenuse. That means that you need to use cosine.

cos 38 = x / 31.8
x = 31.8 cos 38 = 25.0587... = 25.1

Choice (2) is the correct answer.




4. The hemisphere below has a radius of 8 cm.


To the nearest cubic centimeter, the volume of the hemisphere is

(1) 201
(2) 268
(3) 1072
(4) 2145

Answer: (3) 1072


Use the formula for the Volume of a Sphere and then take half of it. The formula is V = (4/3) π r3.

So V = (1/2) (4/3) π (8)3 = 1072.33...

Choice (3) is the correct choice.

If you'd forgotten the 1/2, you would've gotten choice (4).

If you'd forgotten the 1/2 AND halved the radius to 4, you would've gotten Choice (2).

If you used π r2, you would've gotten Choice (1).
Yes, I needed to figure that one out. I wanted to know!




5. In parallelogram ABCD, diagonals AC and BD intersect at E. Which information is sufficient to prove ABCD is a rhombus?

(1) AE ≅ EC
(2) AC ≅ BD
(3) AB ⊥ BC
(4) AC ⊥ BD

Answer: (4) AC ⊥ BD


In a parallelogram, if the two diagonals are perpendicular, then the parallelogram is a rhombus.




6. Trapezoid JOSH, shown below, has non-parallel sides JH and OS, m∠J = 65°, m∠O = 30°, m∠OSA = 80°, and m∠SHU = 60°.



(1) 55°
(2) 60°
(3) 65°
(4) 70°

Answer: (4) 70°


SAO is a triangle, and the sum of its angles is 180 degrees. Because m∠O = 30° and m∠OSA = 80°, then m∠OAS = 70°. Angle OAS and angle HSA are alternate interior angles. Since JO || SH, then ∠OAS ≅ ∠OSA.

Therefore, m∠OSA = 70°, which is Choice (4).




7. In △ABC below, points D and E are on such that AC. DE || AC.

If AD = 8, DB = 4, and DE = 6, what is the length of AC



(1) 24
(2) 18
(3) 12
(4) 10

Answer: (2) 18


The two triangles are have sides that are proportional because they are similar triangles. If AD = 8 and DB = 4, then AB = 12, and the scale factor is 3.

Therefore, if DE = 6 then AC = 6 * 3 = 18.

Choice (2) is the correct answer.




8. On the set of axes below, circle C has a center with coordinates (2,–1).

Which equation represents circle C?



(1) (x - 2)2 + (y + 1)2 = 25
(2) (x - 2)2 + (y + 1)2 = 16
(3) (x + 2)2 + (y - 1)2 = 25
(4) (x + 2)2 + (y - 1)2 = 16

Answer: (1) (x - 2)2 + (y + 1)2 = 25


The formula for the equation of a circle is (x - h)2 + (y - k)2 = r2, where (h,k) is the coordinates of the center and r is the length of the radius.

The center point C is at (1,-2), so eliminate Choices (3) and (4).

If you count across from C, you'll see that the radius is 5. (5)2 = 25, so the correct answer is Choice (1).


More to come. Comments and questions welcome.


MY NEWEST BOOK IS OUT


Burke's Lore Briefs: Yesterday's Villains, the following to Tomorrow's Heroes is now available on Amazon and Kindle Unlimited.

If Heroes who don't die live long enough to become the villain, what happens to Villains who live long enough? When do schemes of global conquest become dreams of a quiet place away from all those annoying people you once wanted to subjugate? And does anyone really want to rule over the world's ashes if it means we can't have nice things?


My older books include three more books in my Burke's Lore Briefs series, and the anthologies A Bucket Full of Moonlight and In A Flash 2020.

Vampires, werewolves, angels, demons, used-car salesmen, fairies, superheroes, space and time travel, and little gray aliens talking to rock creatures and living plants.

Plus pirates, spies, horror, and kindergarten noir!

If you enjoy my books, please consider leaving a rating or review on Amazon or on Good Reads. Thank you!


Thursday, February 19, 2026

Geometry Problems of the Day (Geometry Regents, June 2025 Part I)



This exam was adminstered in June 2025.

More Regents problems.

June 2025 Geometry Regents

Part I

Each correct answer will receive 2 credits. No partial credit.


17. Point O divides COA such that CO:OA = 1:4. If C has coordinates (–2, –9) and A has coordinates (3,6), the coordinates of O are

(1) (2,3)
(2) (1,0)
(3) (0,-3)
(4) (-1,-6)

Answer: (4) (-1,-6)


Dividing 1:4 means that there are 5 parts, with CO being 1/5 of the length COA and OA being 4/5 of the length. Find 1/5 of the change in x values and 1/5 of the change of y values and add those values to (-2,-9).

1/5(3 - -2) = 1/5(5) = 1. 1/5(6 - -9) = 3.

(-2 + 1, -9 + 3) = (-1, -6), which is choice (4).

Another formula you can use is this:

4/5(-2,-9) + 1/5(3,6)
(-8/5, -36/5) + (3/5, 6/5)
(-5/5, -30/5)
(-1, -6)

Remember to put the 4/5 in front of the first coordinate and the 1/5 in front of the second.

This always works.




18. A spherical balloon is fully inflated with helium to a diameter of 1.7 feet. If helium costs $0.80 per cubic foot, what is the cost to completely fill the balloon with helium?

(1) $2.06
(2) $2.42
(3) $3.22
(4) $16.46

Answer: (1) $2.06


Find the volume of the sphere and then multiply by 0.80.

The volume of a sphere is V = 4/3 π r3

V = 4/3 (3.141592...)(.85)3 = 2.57244...

Multiply that by $0.80 = 2.0579..., which rounds to $2.06.




11. In right triangle ABD below, altitude BC is drawn to hypotenuse AD, AC = 2.5, and CD = 4.3.


What is the length of BA, to the nearest tenth?

(1) 3.3
(2) 3.4
(3) 4.1
(4) 5.4

Answer: (3) 4.1


The three right triangles are all similar and their sides are proportional. That means that AC / AB = AB / AD (short leg / hypotenuse).

2.5 / x = x / (2.5 + 4.3)
x2 = 17
x = 4.123...

This rounds to 4.1, which is Choice (3).




20. Trapezoid ZOYD has parallel sides ZO and DY. If m∠Z = 141° and m∠Y = 73°, what is m/D?

(1) 39°
(2) 73°
(3) 107°
(4) 141°

Answer: (1) 39°


If ZO and DY are parallel sides, then OY and DZ are the other two sides. The sum of the measures of angles O and Y must be 180 degrees, and the sum of the measures of angles D and Z must be 180 degrees.

180 - 141 = 39.

Choice (1) is the correct answer.




21. Triangle ABC is translated 5 units to the left and 2 units up to map onto △PQR. Which statement is not always true?

(1) △PQR ≅ △ABC
(2) ∠A ≅ ∠Q
(3) BQ = √(29)
(4) RQ = CB

Answer: (2) ∠A ≅ ∠Q


In a translation, size and shape are preserved. The corresponding angles will be congruent. However, in ABC and PQR, angles A and Q are NOT corresponding angles. They do not have to be congruent. They could be if the triangle is isosceles or equilateral.

In Choice (1), the triangles are always congruent. Eliminate Choice (1).

In Choice (3), point B moves 5 left and 2 up to point Q, so line segment BQ would be √(5^2 + 2^2), which is √(29). Eliminate Choice (3).

In Choice (4), RQ corresponds to CB, so length is preserved. Eliminate Choice (4).




22. In the diagram below, congruent triangles PEN and PAL are drawn.


Which rigid motion maps nPEN onto nPAL?

(1) a point reflection of △PEN through P
(2) a reflection of △PEN over the angle bisector of ∠EPA
(3) a rotation of △PEN about point P, mapping PE onto PA
(4) a translation of △PEN along EA, mapping point E onto A

Answer: (2) a reflection of △PEN over the angle bisector of ∠EPA


The triangles do not have the same orientation. There is a reflection involved.

A point reflection would be 180 degrees about point P. Eliminate Choice (1).

A reflection over the a line bisect the image will carry PEN onto PAL. Choice (2) is the correct answer.

A rotation mapping PE to PA would not move N to point L. The result would be a kite. Eliminate Choice (3).

A translation would not change the orientation. Moving E to A would create a bowtie-like image. Eliminate Choice (4).




23. A cone has a height of 8 inches and volume of 75.4 cubic inches. What is the diameter of the cone, to the nearest inch?

(1) 9
(2) 2
(3) 3
(4) 6

Answer: (4) 6


Use the formula for the volume of a cone, substitute what you know, and solve for the unknown.

The formula for the volume of a cone is V = 1/3 π r2 h.

V = 1/3 π r2 h
75.4 = 1/3 π r2 (8)
r2 = (3) 75.4 / (8 π)
r2 = 9.00...
r = 3

So the DIAMETER is 2 * 3 = 6, which is Choice (4).




24. The line represented by the equation 5x - 2y = 10 is transformed by a dilation centered at (2,0) with a scale factor of 2. The image of the line

(1) is the original line
(2) passes through the point (4,0)
(3) passes through the point (0,–10)
(4) is perpendicular to the original line

Answer: (4) are congruent


A dilation of a straight line will be a parallel line or the same line if the center of dilation is on the line itself. The image cannot be have a different slope, so it cannot be perpendicular. Eliminate Choice (4).

Substitute (2,0) into the original question: 5(2) - 2(0) = 10. This is a true statement, so (2,0) is a point on the original line. Therefore, the image will be the same line. Choice (1) is the correct answer.


End of Part I. Comments and questions welcome.


MY NEWEST BOOK IS OUT


Burke's Lore Briefs: Yesterday's Villains, the following to Tomorrow's Heroes is now available on Amazon and Kindle Unlimited.

If Heroes who don't die live long enough to become the villain, what happens to Villains who live long enough? When do schemes of global conquest become dreams of a quiet place away from all those annoying people you once wanted to subjugate? And does anyone really want to rule over the world's ashes if it means we can't have nice things?


My older books include three more books in my Burke's Lore Briefs series, and the anthologies A Bucket Full of Moonlight and In A Flash 2020.

Vampires, werewolves, angels, demons, used-car salesmen, fairies, superheroes, space and time travel, and little gray aliens talking to rock creatures and living plants.

Plus pirates, spies, horror, and kindergarten noir!

If you enjoy my books, please consider leaving a rating or review on Amazon or on Good Reads. Thank you!