John and Sam have to complete 5 home repair jobs this week. If John works by himself, he can do the repairs in 9 days. With Sam helping him, they completed them in 4 days. How long would it take Sam to complete the repairs alone?
2007-12-18 07:38:54 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Together they did 1/4 of the work each day. Alone John did 1/9 of the work each day. So Sam's contribution is (1/4) - (1/9) or simply 5/36 each day so it would have taken him 36/5 days or 7.2 days.
2007-12-18 07:42:18 · answer #1 · answered by Tim C 7 · 0⤊ 0⤋
John and Sam have to complete 5 home repair jobs this week.
>If John works by himself, he can do the repairs in 9 days.
John 's effort â1/9: 1/j = 9
>With Sam helping him, they completed them in 4 days.
John+ Sam's effort â1/4: 1/(j+s) = 4
>How long would it take Sam to complete the repairs alone?
Want to find 1/s
1/(j+s) = 4 => j+s = 1/4
1/j = 9 => j = 1/9
=> s = (j+s) - j = 1/4 - 1/9 = 5/36
1/s = 36/5
=> Sam alone would take 7 1/5 days
2007-12-18 15:41:34 · answer #2 · answered by smci 7 · 1⤊ 0⤋
5 days?
2007-12-18 15:42:03 · answer #3 · answered by bullitteast54 1 · 0⤊ 0⤋