1 | When radious of a circle is increased by 100 % , then area of the circle increase by A. 200 % B. 100 % C. 300 % D. 400 % Answer : C. 300 % Explanation: \({\pi r^2(4-1) \over \pi r^2} \times 100=300 \%\) |
2 | A fruit seller had some apples. He sells 40% apples and still has 420 apples. Originally, he had: A. 588 apples B. 600 apples C. 672 apples D. 700 apples Answer : D. 700 apples Explanation: Suppose originally he had x apples. Then, (100 - 40)% of x = 420. =>\({60 \over 100} \times x =420\) => \(\bigg ( {420 \times 100 \over 60} \bigg )=700\) |
3 | If the price of petrol increases by 25% and Benson intends to spend only an additional 15% on petrol, by how much % will he reduce the quantity of petrol purchased? A. 8 % B. 7 % C. 10 % D. 6 % Answer : A. 8 % Explanation: Assume that the initial price of 1 Litre petrol = Rs.100 ,Benson spends Rs.100 for petrol, such that Benson buys 1 litre of petrol After the increase by 25%, price of 1 Litre petrol = 100×\((100+25)\over100\)=Rs.125 Since Benson spends additional 15% on petrol, amount spent by Benson = 100×\((100+15)\over 100\)=Rs.115 Hence Quantity of petrol that he can purchase = \(115 \over125\) Litre Quantity of petrol reduced = (1−\(115 \over125\)) Litre Percentage Quantity of reduction = \({(1−{115 \over125})}\over1\)×100 =\(10 \over125\)×100=\(10 \over5\)×4=2×4=8% |
4 | An inspector rejects 0.08% of the meters as defective. How many will be examine to project ? A. 250 B. 2500 C. 25000 D. 250000 Answer : B. 2500 Explanation: Let the number of meters to be examined be x. Then, 0.08% of x =2 \([({8 \over 100}) \times({1\over100}) \times x] = 2\) \(x = \bigg[{(2\times100 \times100) \over8}\bigg]\) = 2500. |
5 | Sixty five percent of a number is 21 less than four fifth of that number. What is the number ? A. 130 B. 135 C. 140 D. 145 Answer : C. 140 Explanation: Let the number be x. Then, \(4 \times {x \over 5}\) –(65% of x) = 21 => \(4{x\over 5} –65 {x \over 100} = 21\) => 15 x = 2100 => x = 140. |
6 | Two students appeared at an examination. One of them secured 9 marks more than the other and his marks was 56% of the sum of their marks. What are the marks obtained by them? A. 42,33 B. 42,36 C. 44,33 D. 44,36 Answer : A. 42,33 Explanation: Let the marks secured by them be \(x\) and \((x+9)\) sum of their marks =\(x+(x+9)=2x+9\) Given that \((x+9)\) was 56% of the sum of their marks. ⇒ \((x+9)={56\over100}(2x+9)\) ⇒ \((x+9)={14\over25}(2x+9)\) ⇒ \(25x+225=28x+126\) ⇒ \(3x=99\) ⇒ \(x=33\) Then \((x+9)=33+9=42\) Hence their marks are 33 and 42 |
7 | If A =x% of yy and B =y% of x , then which of the following is true? A. None of these B. A is smaller than B. C. Relationship between A and B cannot be determined. D. A is greater than B. Answer : A. None of these Explanation: \(A={x\over 100} \times y={xy\over 100}.......(1)\) \(B={y\over 100} \times x={yx\over 100}.......(2)\) Therefore A = B |
8 | If 20% of a = b, then b% of 20 is the same as: A. None of these B. 10% of a C. 4% of a D. 20% of a Answer : C. 4% of a Explanation: 20% of a=b ⇒ \(b={20a \over 100}={a\over5}\) b% of 20 = \(20 \times {b\over 100}\) \(={b\over5}={a\over5} \times {1\over 5}= {a\over 25}\) \(={4a \over 100}=4\%\) of a |