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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 8

A can do a work In 45 days. He works at it for 15 days and then, B alone finishes the remaining work in 24 days. Find the time taken to complete 80% of the work, if they work together - Mathematics

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Question

A can do a work In 45 days. He works at it for 15 days and then, B alone finishes the remaining work in 24 days. Find the time taken to complete 80% of the work, if they work together

Sum
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Solution

A complete the work in 45 days.

∴ A’s 1 day work = `1/45`

A's 15 days work = `15/45 = 1/3`

Remaining work = `1 - 1/3 = (3 - 1)/3 = 2/3`

B finishes `2/3` rd work in 24 days

B's 1 day work = `(2/3)/24`

= `2/(3 xx 24)`

= `1/36`

(A + B)'s 1 day work = `1/45 + 1/36`

9 45, 36
5, 4

= `(4 + 5)/180`

= `9/180`

= `1/20`

Let x days required

∴ `x/20 = 80/100`

⇒ x = `80/100 xx 20`

= 16 days

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Chapter 4: Life Mathematics - Exercise 4.4 [Page 151]

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Samacheer Kalvi Mathematics [English] Class 8 TN Board
Chapter 4 Life Mathematics
Exercise 4.4 | Q 9 | Page 151

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