Thanks to Daneesha for the suggestion! This question from Sri Lanka’s 2021 G.C.E A/L Combined Maths exam paper had an error that the test makers overlooked!

The figure below consists of a rectangle and two attached circular sectors. All length dimensions are in meters. The area of the entire shape is 36 m2. Show the perimeter p is given by p = 2x + ( Read more... )

This is a fun Cambridge entrance exam question (UCLES STEP Mathematics I, 2009, Q1).

A proper factor of an integer N is a positive number that divides N but is not equal to 1 or N.

(A) Show that 32×53 has exactly 10 proper factors.

(B) How many other integers of the form 3m×5n have exactly 10 proper factors? (m, n are integers)

(C) What is the ( Read more... )

I present a video to show how you can use your fingers to:

-multiply numbers from 6 to 9
-multiply numbers from 11 to 15
-remember the times table for 9

Finger Multiplication 3 Tricks

0:00 intro
0:23 multiply 6 to 9
7:18 why works 6 to 9
11:52 multiply 11 to 15
15:40 why works 11 to 15
17:14 times table 9
19:28 why works table 9

Or keep reading.

.
.
.
.
M
I
N
D
.
Y
( Read more... )

Note to long-time readers: Puzzle 1 is a new problem. Puzzles 2 and 3 are re-posts added to this compilation. (YouTube is preferring longer videos, and it is a good time to re-share overlooked problems.)

Puzzle 1

This is adapted from a 6th grade cram school problem in China. A solid figure is made by stacking several cubical blocks with a side ( Read more... )

This is a fun problem that comes from a math competition. The two circles with radii r and s have common tangents of AB and PQ. The length of PQ is 14 units and the length of AB is 16 units. What is the value of rs ?


( Read more... )

The SAT in America is a standardized test used for admission to college. Today the test focuses on the two areas Reading & Writing and Math. The very first test had 10 sections covering a range of questions. How well would you do on the test?

The video includes a sample of the 390 questions the students had to cover in about 2 hours (about 20 ( Read more... )

This is a fun little problem. Each shape represents a different digit from 0 to 9. What is the value of each shape?


( Read more... )

Inside of rectangle ABCD is a triangle AMN with M along BC and N along CD. Suppose BM = 6 cm, ND = 4 cm, and the area of AMN = 70 cm2. What is the area of the rectangle ABCD ?


( Read more... )

How many of these 7 puzzles can you solve?

Puzzle 1


( Read more... )