Primes, squares and roots N1.5 Extension Starter Look at the grid and find numbers which fit each condition. The largest prime number. Three consecutive numbers. Three numbers which round to 30. The square root of 81. The row with the smallest total. Two numbers whose product is 100. A number divisible by 19. Two numbers which sum to 70. Three triangular numbers. Preamble This fairly standard target board activity probes pupils’ recall of number vocabulary and properties. It lends itself to using pupil white boards to produce rapid responses. It can be extended by asking different questions or by asking pupils to think up their own questions which have answers on the target board. Possible content Various number properties including prime number, triangle number and square root. Resources Pupil white boards. Solutions/Notes 1. The largest prime number is 61. Three consecutive numbers are 19, 20, 21 or 20, 21, 22. Three numbers which round to 30 are 28, 34 and 25. The square root of 81 is 9. The row with the smallest total is the 4th row. The total is 94. Two numbers whose product is 100 are 4 and 25. Numbers divisible by 19 are 19 and 38. Pairs which sum to 70 are 34 and 36, 42 and 28, 48 and 22, 61 and 9, and 64 and 6. The triangular numbers are 1, 6, 15, 21, 28 and 36.