# Important Formulas

# Problems on Time and Work

Q31. A and B can finish a piece of work in 30 days. They worked at it for 20 days and then B left. The remaining work was done by A alone in 20 more days. A alone can finish the work in

(a) 47 days

(b) 52 days

(c) 60 days

(d) 72 days

**Answer:** (c) 60 days

Work done by (A+b) in 20 days = (1/30) X 20 = 2/3

Remaining work = 1 - | 2 | = | 1 |

3 | 3 |

1/3 work is done by A in 20 days

∴ whole work is done by A in (20 X 3) = 60 days

Q32. A and B undertook to do a piece of work for Rs. 4500. A alone should do it in 8 days and B alone in 12 days. With the assistance of C they finished the work in 4 days. C's share of money is

(a) Rs. 695

(b) Rs. 710

(c) Rs. 750

(d) RS. 800

**Answer:** (c) Rs. 750

A's 1 day's work = 1/8

B's 1 day's work = 1/12

(A+B+C)'s 1 day's work = 1/4

∴ C's 1 day's work = | 1 | - ( | 1 | + | 1 | ) = | 1 | - | 5 | = | 1 |

4 | 8 | 12 | 4 | 24 | 24 |

∴ A : B : C = 1/8 : 1/12 : 1/24 = 3 : 2 : 1

C's share = Rs. (4500 X 1/6) = Rs. 750