请教2道数学题

1. function h(n) is defined to be product of all even integers from 2 to n, inclusive.if p is the smallest prime factor of h(100)+1, then p is

a) btween 2 and 10 b)btw 10-20 c)20-30 d)30-40 e)>40

answer is e

2. DS: combined x tons of gravel mixture that contained 10% gravel G, by weight, with  y tons of mixture contain 2% of gravel G, to produce z tons of mixture 5% gravel G. what is the value x?

1) y=10  2) z=16 

answer is d

3X!

第一題簡單的說，h(n)=2*4*6*8*.....*n，其中n是某個偶數

所以h(100)+1=2*4*6*8*...*100+1 = 2*(1*2*3*...*50)+1

因此前50個整數都不是該數的因數，所以至少p>50，以原題來說就是選項(E)符合