- Rational Numbers
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- Playing with Numbers
- Operations on Algebraic Expressions
- Factorisation
- Linear Equations
- Percentage
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- Compound Interest
- Direct and Inverse Proportions
- Time and Work
- Polygons
- Parallelograms
- Construction of Quadrilaterals
- Area of a Trapezium and a Polygon
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- Volume and Surface Area of Solids
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RS Aggarwal Solutions Class 8 Mathematics Solutions for Time and Work Exercise 13A in Chapter 13 - Time and Work
Prev
A and B can finish a piece of work in 16 days and 12 days respectively. A
started the work and worked at it for 2 days. He was then joined by B. Find
the total time taken to finish the work.
we know that,
Number of days A required to do a piece of work = 16days
Number of days B required to do a piece of work = 12days
∴ We can calculate, work done by A in 1 day = 1/16
Work is done by B in 1 day = 1/12
Alone works for 2 days and the work completed by A in 2 days = 2 × 1/16 = 1/8
∴ work left = 1- 1/8 = 7/8
Work done by A, B together in a one day = 1/16 + 1/12 = 7/48
∴ they can work together in 48/7 days
But 7/8th work is completed by both A and B
∴ the time required to complete 7/8th work together by A and B = 7/8 × 48/7 = 6days
Time is taken to finish the work = 6 + 2 = 8days(2 is added because 1/8 work is done by A
alone)
∴ The total time is taken to complete the work =8days.
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