question 18 page 171 number properties guide.

[lawsongive]

I don't understand why 30 is not included in one of the answers?

if X = 30 then the squared term is 900 which is divisible by both 40 and 75 and the prime factors are 2, 2, 3, 3, 5, 5 (twice the ones for 30)?

or is this another way of saying the squared term has to be greater than 40 X 75 = 3000? (which 900 is not)?

Thanks

[tommywallach]

Hey Lawson,

Be careful! 900 is NOT actually divisible by 40. 40 divides evenly into all multiples of 200, but not all multiples of 100.

-t