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secondary 3 | E Maths
2 Answers Below
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Pls help with 5c ONLY thanks in advance
Date Posted: 3 years ago
Views: 191
Simple.
Fraction of work Jared does in 1 minute = 1/x
Fraction of work Michael does in 1 minute = 1/(x + 15)
Together, they will do 1/x + 1/(x + 15) of the work in 1 minute.
Since they will finish in 20 minutes, then in 1 minute, they will do only 1/20 of the work.
So,
1/x + 1/(x + 15) = 1/20
(x + 15 + x)/(x(x + 15)) = 1/20
(2x + 15)/(x² + 15x) = 1/20
Cross multiply,
20(2x + 15) = x² + 15x
40x + 300 = x² + 15x
x² + 15x - 40x - 300 = 0
x² - 25x - 300 = 0
Fraction of work Jared does in 1 minute = 1/x
Fraction of work Michael does in 1 minute = 1/(x + 15)
Together, they will do 1/x + 1/(x + 15) of the work in 1 minute.
Since they will finish in 20 minutes, then in 1 minute, they will do only 1/20 of the work.
So,
1/x + 1/(x + 15) = 1/20
(x + 15 + x)/(x(x + 15)) = 1/20
(2x + 15)/(x² + 15x) = 1/20
Cross multiply,
20(2x + 15) = x² + 15x
40x + 300 = x² + 15x
x² + 15x - 40x - 300 = 0
x² - 25x - 300 = 0
Edited
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Hope you understand :)
Date Posted:
3 years ago
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