SAT Question of the Day June 12 2013

A geologist has 10 rocks of equal weight. If 6 rocks and a 10-ounce weight balance on a scale with 4 rocks and a 22-ounce weight, what is the weight, in ounces, of one of these rocks?

A.     4

B.     5

C.     6

D.     7

E.     8

All we need to do is to set an equation – one rock will weigh X ounces.

6X+10=4X+22

It is clear we have two more rocks on one side and 12 ounce more on the other.

This implies each rock weighs 6 ounces.

71% out of 128,000 got it right – indeed a relatively simple question.

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