: Get your basic arithmetic concepts right #IndiaNEWS #Education Today By Banda Ravipal Reddy Director, SIGMA Sai Institute of General Mental Ability Hyderabad This article is in continuation to the

Get your basic arithmetic concepts right #IndiaNEWS #Education Today
By Banda Ravipal Reddy
Director, SIGMA
Sai Institute of General Mental Ability
Hyderabad
This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some previous year questions and explanations on the Time and Work topic. To improve calculations speed, the aspirants must practice questions from the previous question papers.
1. Two persons have undertaken to do a piece of work for Rs 1,200. One alone could it in 6 days and the other in 8 days. With the assistance of a boy, they finish it in 3 days. The difference between the shares of the two persons (in rupees) is (SI 2016).
A. 150. 200 C. 25 D. 300
Ans: A
Explanation:
First person 1 days work = 1/6 Second person 1 days work = 1/8 Let boys 1 days work be 1/x According to the question, ? (1/6) (1/8) (1/x) = (1/3)? (1/x) = (1/3) {(1/6) (1/8)} ? (1/x) = 1/24 ? Ratio in shares of first person, second person and boys = (1/6): (1/8): (1/24) = (1/6) × 24: (1/28) × 24: (1/24) × 24 = 4: 3: 1 The difference between shares of the two person = {(4 3)/(4 3 1)} × 1200 = 150
2. Two men undertaken to do a piece of work for Rs. 5,600. First man alone can do this work in 7 days while the second man alone can do this work in 8 days. If they work together and complete this work in 3 days with the help of a boy, then the amount the two men together get is (in rupees).
A. 4,000 B. 4,500 C. 4,580 D. 4,600
Ans: B
Explanation:
First mans 1 days work = 1/7 Second mans 1 days work = 1/8 Boys 1 days work = (1/3) {(1/7) (1/8)} = (1/3) (15/56) ? Boys 1 days work = (11/168) ? Ratio of wages of the first man, second man and boy = (1/7): (1/8): (11/168) L. C. M of 7, 8, and 168 is 168 Ratio of wages of the first man, second man and boy = (1/7) × 168: (1/8) × 168: (11/168) × 168 ? Ratio of wages of the first man, second man and boy = 24: 21: 11 ? Total share of the amount = 24 21 11 = 56 units ? First mans share = Rs (24/56) × 5600 = Rs 2400 ? Second mans share = Rs (21/56) × 5600 = Rs 2100 The amount shares in two men together get = 2400 2100 = 4500 ? the amount the two men together get is Rs 4500
3. If the wages of 6 men for 15 days be Rs. 700, then the wages of 9 men for 12 days will be (in rupees).
A. 840 B. 848 C. 1,050D. 900
Ans: A
Explanation:
Let the required wages be Rs x. More men, more wages (direct proportion) Less days, less wages (direct proportion) men 6: 9 : : 700: x Days 15:12 Therefore (6 × 15 × x) = (9 × 12 × 700) =>; x = (9 × 12 × 700)/(6 ×15) = 840 Hence, the required wages are Rs 840 . men can do a work in 12 days.