Explain why `7xx11 xx 13 + 13 and 7 xx 6xx 5 xx 4 xx 3 xx 2xx 1 +5` are composite numbers.

7xx11xx13+13 is a composite number. Why ?

Is 7 xx 5 xx 3 xx 2 + 3 a composite number? Justify your answer.

Explain why (7 times 11 times 13)+13 " and " (7 times 6 times 5 times 4 times 3 times 2 times 1)+5 are composite numbers.

Take any three consecutive odd numbers and find their product, for example 1 xx 3 xx 5 = 15 , 3 xx 5 xx 7 = 105 , 5 xx 7 xx 9=315 and so on. Make three conjuctures about these products.

If A={-1,1}, find A xx A xx A

If A={-1,1}, find A xx A xx A .

How will you show that (17xx11xx2)+(17xx11xx5) is a composite number? Explain.

Explain Why 7times11times13times+13 and 7times6times5times4times3times2times1times+5 are composite number.

(b) Find the sum to n terms of the series 1 xx 2 xx 3 + 2 xx 3 xx 4 + 3 xx 4 xx 5 + .. .

Simplify: 7^2 xx 2^2