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Mohan Takes 16 Days Less than Manoj to Do a Piece of Work. If Both Working Together Can Do It in 15 Days, in How Many Days Will Mohan Alone Complete the Work? - ICSE Class 10 - Mathematics

Question

Mohan takes 16 days less than Manoj to do a piece of work. If both working together can do it in 15 days, in how many days will Mohan alone complete the work?

Solution

Let the number of days in which Mohan completes the works be x

Number of days in which Manoj completes the work = x + 16

In one day, Mohan completes 1/x parts of work.

In one day, Manoj completes 1/(x + 16) parts of work

It is given that they both can do the work in 15 days.

∴ 1/x + 1/(x  +  16) = 1/15

(x  + 16 + x)/(x(x + 16)) = 1/15

(2x + 16)/(x ^2 + 16x) = 1/15

30x + 240 = x^2 + 16x

x^2 - 14x - 240 = 0

x^2 - 24x + 10x - 240 = 0

x(x - 24) + 10(x - 24) = 0

(x - 24) (x + 10) = 0

Since the number of days cannot be negative So x = 24

Thus  Mohan alone can complete the work in 24 days

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Selina Solution for Selina ICSE Concise Mathematics for Class 10 (2018-2019) (2017 to Current)
Chapter 6: Solving (simple) Problems (Based on Quadratic Equations)
Ex.6E | Q: 11

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Solution Mohan Takes 16 Days Less than Manoj to Do a Piece of Work. If Both Working Together Can Do It in 15 Days, in How Many Days Will Mohan Alone Complete the Work? Concept: Quadratic Equations.
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