Let v be the velocity of the boat
Then:
90/(v-3) - 90/(v+3) = 0.5
or 90(v+3) - 90(v-3) = 0.5 (v2-9)
Solving we get v2 = 1089
or v = 33 (+/-), but we ignore the minus value.
And hence 90/v+3 = 2.5 hours
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Source: Beat The GMAT — Problem Solving |
Can you walk me through this reduction? Thanks.
or 90(v+3) - 90(v-3) = 0.5 (v2-9)
Solving we get v2 = 1089
or 90(v+3) - 90(v-3) = 0.5 (v2-9)
Solving we get v2 = 1089
