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Brainteasers

Sum fun

Age 5-7

Use two + signs and two - signs.

Put them in the boxes to make the sums correct.

Minimum lines

Age 11-14

This rectangle has 9 straight lines and 14 squares. Can you find them all?

This one has 9 straight lines and 20 squares. Can you find them all?

Find the minimum number of lines needed to make a rectangle with exactly 100 squares.

BRAINTEASER SOLUTIONS

Sum fun

For example:

a. 5 - 4 + 3 + 2 - 1 = 5

b. 2 + 2 - 3 + 4 - 5 = 0

Minimum

A minimum of 15 lines are needed to form exactly 100 squares in an 8 by 5 rectangle

The total number of squares is (8 x 5) + (7 x 4) + (6 x 3) + (5 x 2) + (4 x 1) = 100

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