# Brainteasers

20th May 2005 at 01:00
Puzzles to test mathematical skills, set by Anita Straker. Solutions below

More brainteasers on www.tes.co.ukteacherbrainteasers

CLOCK FACE PUZZLES

This clock face has been divided into two sectors.

This sum of the numbers is one sector is 30 and in the other sector is 48.

1 Divide the clock face into two sectors, so that the sum of the numbers in each sector is the same.

2 Divide the clock face into three sectors, so that the sums of the numbers in each sector form three consecutive numbers.

Jade chose a positive whole number.

She multiplied it by 2, added on 5, then multiplied by the original number.

The result was 403.

SOLUTIONS Clock face puzzles (age 7-12) 1. 10, 11, 12, 1, 2, and 3 sum to 39; 4, 5, 6, 7, 8 and 9 also sum to 39. The sum of the numbers 1 to 12 is 78; if the numbers in the two sectors have equal totals, each must be 39.

2. 3, 4, 5, 6 and 7 sum to 25; 11, 12, 1 and 2 sum to 26; 8, 9 and 10 sum to 27. The middle consecutive number must be one third of 78, or 26, so the consecutive numbers are 25, 26 and 27.

Jade's number (age 9-12) 13. As the last operation was to multiply by the original number, that number must be a factor of 403. 403 = 13 x 31. Trying 13 and 31, we get (13 x 2 + 5) x 13 = 403, but (31 x 2 + 5) x 31=2077.

Not a subscriber? Find out more about our subscription offers.
Subscribe now
Existing subscriber?
Enter subscription number