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RD Sharma Solutions Class 8 Mathematics Solutions for Time and Work Exercise 11.1 in Chapter 11 - Time and Work

Question 9 Time and Work Exercise 11.1

A, B and C can reap a field in 15 ¾ days; B, C and D in 14 days; C, D and A in 18days; D, A and B in 21 days. In what time can A, B, C and D together reap it?

Answer:

The given details are,

A, B and C can reap the field in = 15 ¾ days = 63/4 days

(A, B and C)’s 1 day work =1/(63/4) = 4/63

B, C and D can reap the field in = 14 days

B, C and D’s 1 day work = 1/14

C, D and A can reap the field in = 18 days

C, D and A’s 1 day work = 1/18

D, A and B can reap the field in = 21 days

D, A and B’s 1 day work = 1/24

Now adding (A+B+C+D),

3[A+B+C+D] = 4/63 + 1/14 + 1/18 + 1/21

= (8+9+7+6)/126

= 30/126

= 5/21

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