1. If x = a + [latex]\frac {1}{a}[/latex] and y = a - [latex]\frac {1}{a}[/latex], then the value of [latex]{x}^{4}[/latex] + [latex]{y}^{4}[/latex] - [latex]2{x}^{2}{y}^{2}[/latex] is
Answer Option C
Explanation :
x + y = a + [latex]\frac {1}{a}[/latex] - a - [latex]\frac {1}{a}[/latex] = 2a
and x - y = (a + [latex]\frac {1}{a}[/latex]) - ( a - [latex]\frac {1}{a}[/latex]) = [latex]\frac {2}{a}[/latex]
i.e, (x + y)(x - y) = 2a [latex]\times \frac {2}{a}[/latex] = 4
[latex]{({x}^{2} -{y}^{2})}^{2} = {4}^{2} = 16[/latex]
[latex]{x}^{4} + {y}^{4} - 2{x}^{2}{y}^{2}[/latex] = 16
2. A radio set, marked 750 is sold at 570. The rate of discount offered is
A. 14 %
B. 34 %
C. 24 %
D. 20 %
Answer Option C
Explanation :
Market rate of radio = ? 750
Selling price of Radio = ? 570
Hence discount = Market Price – selling price
Discount = 750 – 570 = 180
Discount % = [latex] \frac {(discount×100)}{market price}[/latex] = [latex] \frac {180 \times 100}{750}[/latex]
= [latex] \frac {360}{15}[/latex] = 24 %
3. A sells an article to B at a gain of 10 %, B sells it to C at a gain of 5 %. If C pays 462 for it, what did it cost to A?
A. 500
B. 450
C. 600
D. 400
Answer Option D
Explanation :
Let price of an article = X
A sells an article to B at a gain of 10 %
Hence A’s profit = [latex] \frac {10 x}{100}[/latex] = [latex] \frac {x}{10}[/latex]
S. P. for A = x + [latex] \frac {x}{10}[/latex] = [latex] \frac {11 x}{10}[/latex]
[latex] \frac {11 x}{10}[/latex] Rs. Is C. P. for B
Now B sells it to C at a gain of 5%.
Hence B’s profit = [latex]5 \times \frac {\frac {11 x}{10}}{100} = \frac {11 x}{200}[/latex]
Hence S. P. for B =[latex]\frac {11x}{10} + \frac {11x}{200} = 220 x + \frac {11x}{200} = \frac {231x}{200}[/latex]Rs
This [latex]\frac {231X}{200}[/latex] Rs is C. P. for C
But given that C pays 462
Therefore
[latex]\Rightarrow X = 200 \times \frac {462}{231}[/latex]
= 200 [latex]\times[/latex] 2 = 400
Hence A cost Rs 400 for article.
4. A sold an article sold for Rs.8,750 with 25% profit on the price he bought. And he bought the article at 30% concession on the marked price. What was the marked price?
A. 13,000
B. 16,000
C. 12,000
D. 10,000
Answer Option D
Explanation :
Let marked Price = 100 unit
CP = 70 unit (30 % discount)
SP = 70 *125/100 = 70 * 5/4 = 350/4 = 87.5 unit
87.5 unit = 8750 Rs
100 unit = 10000 Rs
5. Is 999 [latex] \frac {998}{999}\times 999[/latex] equal to:
A. 998999
B. 999899
C. 989999
D. 999989
Answer Option A
Explanation :
999 [latex] \frac {998}{999}\times 999[/latex]
[latex](999 + \frac {998}{999})\times 999[/latex]
[latex] {999}^{2} + 998[/latex]
[latex] {(1000 - 1)}^{2} + 998[/latex]
= 1000000 - 2000 + 1 + 998
= 998999
6. The whole surface of a cube is 150 sq. cm. Then the volume of the cube is
A. 125 [latex]{cm}^{3}[/latex]
B. 216 [latex]{cm}^{3}[/latex]
C. 343 [latex]{cm}^{3}[/latex]
D. None of these
Answer Option A
Explanation :
Whole surface of a cube is =150
or, 6[latex]{a}^{2}[/latex] = 150
a = 5
So, Volume of cube = [latex]{a}^{3}[/latex]= 125
7. Acid and water are mixed in a vessel A in the ratio of 5:2 and in the vessel B in the ratio 8:5. In what proportion should quantities be taken out from the two vessels so as to form a mixture in which the acid and water will be in the ratio of 9:4?
A. 7:2
B. 2:7
C. 7:4
D. 2:3
Answer Option A
Explanation :
Let the amount of mixture in vessels A and B are X and Y Liters respectively. [latex] \frac {5X}{7}[/latex]
Hence amount of acid in vessels A = [latex] \frac {5X}{7}[/latex]
Amount of water in vessel A = [latex] \frac {2X}{7}[/latex]
Hence amount of acid in vessels B = [latex] \frac {8Y}{13}[/latex]
Amount of water in vessel B = [latex] \frac {5Y}{13}[/latex]
Therefore amount of acid in vessel C = ([latex] \frac {5X}{7}[/latex]) + ([latex] \frac {8Y}{13}[/latex]) = [latex] \frac {(65X + 56Y)}{91}[/latex]
Therefore amount of water in vessel C = (2X/7) + (5Y/13) = (26X + 35)/91
Given: [latex] \frac {(65X + 56Y)}{91}[/latex] : [latex] \frac {(26X + 35Y)}{91}[/latex] = 9 : 4
4(65X + 56Y) = 9(26X + 35Y)
260X + 224Y = 234X + 315Y
26X = 91Y [latex]\rightarrow \frac {X}{Y}[/latex]
= [latex] \frac {91}{26}[/latex]
= [latex] \frac {7}{2}[/latex]
X : Y = 7 : 2 [latex] \frac {(26X + 35Y)}{91}[/latex]
8. The greatest value among the fractions [latex] \frac {2}{7}, \frac {1}{3}, \frac {5}{6}, \frac {3}{4} [/latex] is:
A. [latex] \frac {3}{4} [/latex]
B. [latex] \frac {5}{6} [/latex]
C. [latex] \frac {1}{3} [/latex]
D. [latex] \frac {2}{7} [/latex]
Answer Option B
Explanation :
[latex] \frac {5}{6}, > \frac {3}{4}, > \frac {1}{3}, > \frac {2}{7} [/latex]
The greatest is [latex] \frac {5}{6}[/latex]
9. A number is greater than thrice its reciprocal by [latex] \frac {26}{3} [/latex]. What is the number?
Answer Option C
Explanation :
Let the number be x
Then its reciprocal will be [latex] \frac {1}{x} [/latex]
[latex]\Rightarrow x - \frac {3}{x} = \frac {26}{3} [/latex]
[latex]3{x}^{2} - 9 - 26x = 0 [/latex]
[latex]3{x}^{2} - 26x - 9 = 0 [/latex]
[latex]3{x}^{2} - 27x + x - 9 = 0 [/latex]
3x (x - 9) + 1 (x - 9) = 0
(x - 9)(3x + 1) = 0
x = 9
10. The printed price of a book is 320. A retailer pays 244.80 for it. He gets successive discounts of 10% and an another
rate. His second rate is :
A. 15%
B. 16%
C. 14%
D. 12%
Answer Option A
Explanation :
The printed price of a book = 320
A retailer pays 244.80 for it
First discount = 10%
Hence discount price =320 [latex]\times \frac {10}{100} [/latex] = 32 Rs
Hence price after first discount = 320 – 32 = ? 288
Let second discount = x%
Price after second discount = 244.80
Hence
[latex]288 \times \frac {x}{100} = 288 - 244.80 = 43.20 [/latex]
[latex]\Rightarrow = 43.20 \times \frac {100}{288} = 15 [/latex]
Hence second % discount = 15%