Question 6
Explain why 7×11×13+13 and 7×6×5×4×3×2×1+5 are composite numbers.
7×11×13+13
Taking 13 common, we get
7×11×13+13=13(7×11+1)
13(77 + 1 )
13 (78)
It is a product of two numbers, both greater than 1. Hence, it is a composite number.
7×6×5×4×3×2×1+5
Taking 5 common, we get
7×6×5×4×3×2×1+5=5(7×6×4×3×2×1+1)
5(1008 + 1)
5(1009)
It is a product of two numbers, both greater than 1. So, it is a composite number.