Greg can milk all of the carabaos in 120 minutes and Harold can do it in 60 minutes. If Greg milks for 20 minutes before Harold joins him, how long would it take them to finish?
Solution:
Let x be the length of time Greg and Harold can finish milking the carabaos.
Rate (job per minute) Time Work
Greg 1/120 x + 20 ( x + 20 ) / 120
Harold 1/60 x x/60
Equation: ( x + 20 ) / 120 + x/60 = 1
To solve, multiply both sides of the equation by the LCD, i.e.
120 ( ( x + 20 ) / 120 + x/60 ) = ( 1 ) 120
x + 20 + 2x = 120
3x + 20 = 120
3x = 120 - 20
3x = 100
x = 100/3
x = 33 1/3 minutes or 13 minutes and 20 seconds.
Therefore, Greg and Harold can milk all the carabaos in 13 minutes and 20 seconds.
Problem is taken from e-math kto12 edition Grade 7
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