Bethany can mow her family’s lawn in 4 hours. Her brother Colin can mow the lawn in 3 hours. Which equation can be used to find the number of hours, x, it would take for Bethany and Colin to mow the lawn together? Rate (Lawns per Hour) Time (Hours) Fraction Completed Bethany 1 fourth x 1 fourth x Colin 1 third x 1 third x
Answer
A
1 fourth x minus 1 third x is equal to 1
B
3 plus 4 is equal to x
C
4 minus 3 is equal to x
D
1 fourth x plus 1 third x is equal to 1
Explanation
Bethany mows 1/4 of the lawn per hour, and Colin mows 1/3 of the lawn per hour. In x hours, they complete x/4 and x/3 of the lawn, respectively. Together they must complete one whole lawn, so the equation is x/4 + x/3 = 1, choice D.
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