Brainteasers

Anita Straker

Puzzles to test mathematical skills, set by Anita Straker. Solutions below More brainteasers on www.tes.co.ukteacherbrainteasers

Life and death

A group of cats, birds and snakes lived in a cave.

One day at breakfast, each cat ate one bird.

At lunchtime, each snake ate one cat.

At tea time, each bird ate one snake.

After tea there was only one bird left.

How many cats, birds and snakes were there in the group?

Make 9

Use only these keys on your calculator, once each, in any order.

(1) (2) (3) (4) (5) (6) (7) (8) (9) (+) (-) (=) When you press the equals key, the number 9 should appear on the display.

Find different ways to do it.

SOLUTIONS Make 9 (age 9 to 14): There are several possible solutions. For example: 128 + 574 - 693 = 9, and variations on this, eg, 528 + 174 - 693 = 9, 178 + 524 - 693 = 9, 578 + 124 - 693 = 9, 124 + 578 - 693 = 9, 524 + 178 - 693 = 9, 174 + 528 - 693 = 9, 574 + 128 - 693 = 9. Another solution is 648 + 153 - 792 = 9

SOLUTIONS Life and death (age 7 to 11): 2 birds, 1 snake and 1 cat.

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