4/19/10

Test 7 Section 7 - #15 (page 788)

It would take us way too long to list all the numbers from 1-100 and check which are perfect squares.  Luckily we don't have to.  All we need to do is count all the ones that ARE, and then we know all the rest are NOT.  To do so, let's just list squares of integers until they get bigger than 100:

12 = 1
22 = 4
32 = 9
42 = 16
52 = 25
62 = 36
72 = 49
82 = 64
92 = 81
102 = 100
112 = 121 (Oops, too big!)

There are 100 numbers between 1 and 100 (inclusive), and we just counted 10 of them that ARE perfect squares. That means 90 are not.  Choice (E) is our answer.

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