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A Group of Labourers Promises to Do a Piece of Work in 10 Days, but Five of Them Become Absent. If the Remaining Labourers Complete the Work in 12 Days, Find Their Original Number in the Group. - Mathematics

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Question

A group of labourers promises to do a piece of work in 10 days, but five of them become absent. If the remaining labourers complete the work in 12 days, find their original number in the group.

Sum

Solution

Total period = 10 days

But work completed in = 12 days

No. of men was absent = 5

Let the number of men in the beginning = x

Now x men can do piece work in = 10 days

1 man will do it in = 10x × days

and (x − 5) will do it in =`(10xx"x")/("x"-5)` days

∴ `(10"x")/("x"-5)=12`

⇒ 10x = 12x − 60

⇒ 12x − 10x = 60 ⇒ 2x = 60

⇒ x =`60/2` = 30

∴ No. of men in the beginning = 30

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Concept for Unitary Method (With Only Direct Variation Implied)
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Chapter 10: Direct and Inverse Variations - Exercise 10 (D) [Page 130]

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Selina Concise Mathematics [English] Class 8 ICSE
Chapter 10 Direct and Inverse Variations
Exercise 10 (D) | Q 12 | Page 130
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