28th January 2005 at 00:00
Puzzles to test mathematical skills, set by Anita Straker. Solutions below More brainteasers on


Use all the odd numbers from 1 to 9.

Put one number in each box of the cross.

The numbers in each line of three must add up to the same total.

Find all the possible totals.

1 3 5 7 9


Jack needed some short lengths of wire for model-making. He bought three pieces, all the same length.

He cut one piece into 4cm lengths and had 1cm of wire left over.

He cut the second piece into 7cm lengths and had 1cm of wire left over.

He cut the third piece into 10cm lengths and had 1cm of wire left over.

What is the shortest possible length of each piece of wire that Jack bought?

SOLUTIONS Magic cross (age 5-7) The possible totals are 17 (with 9 in the middle), 15 (with 5 in the middle) and 13 (with 1 in the middle)

Cutting the wire (age 10-14) The shortest possible length is 141cm. The lowest common multiple of 4, 7 and 10 is 140. Since 1cm of wire was left over each time, each piece was 141cm.

Log-in as an existing print or digital subscriber

Forgotten your subscriber ID?


To access this content and the full TES archive, subscribe now.

View subscriber offers


Get TES online and delivered to your door – for less than the price of a coffee

Save 33% off the cover price with this great subscription offer. Every copy delivered to your door by first-class post, plus full access to TES online and the TES app for just £1.90 per week.
Subscribers also enjoy a range of fantastic offers and benefits worth over £270:

  • Discounts off TES Institute courses
  • Access over 200,000 articles in the TES online archive
  • Free Tastecard membership worth £79.99
  • Discounts with Zipcar,, Virgin Wines and other partners
Order your low-cost subscription today