# Brainteasers

Ages 7-11

Find the pattern

The letters A to J stand for 10 numbers in a number pattern.

The sum of any three adjacent numbers in the pattern is 10.

B is 2, and J is 5.

What are the 10 numbers?

Ages 11-14

Ring of good fortune

Six equal small circles are drawn in contact with a large circle as shown.

The radius of the large circle is 12cm.

What is the radius of the small circles?

SOLUTIONS Ring of good fortune The radius of the smaller circle is 4cm.

Triangle OAB is equilateral, so OB is twice the radius of the small circle.

BR equals the radius of the small circle. So the radius of the large circle is three times the radius of the small circle.

SOLUTIONS Find the pattern JJJ If B is 2, then C + D = 8, E = 2, F + G = 8, * = 2 and I+J=8. Since J = 5, I = 3. Since I = 3 and H = 2, G = 5. Since F + G = 8 and G = 5, F = 3. Since F = 3 and E =2, D = 5. Similarly, it follows that C = 3 and A = 5.

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