1. A train 575 m long crosses a tunnel of length 325 in 90 sec. What is the speed of the train in kmph.
Answer: 36
Explanation:Total distance traveled = Length of train + Length of tunnel
= 575 + 325 = 900.
Time taken to cross the tunnel = 90 sec.
Speed in kmph = distance/time * 18/5 = 900/90 * 18/5 = 180/5 = 36 kmph.
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2. Three partner's A,B,C start a business. Twice A's capital is equal to thrice B's capital and B's capital is four times C's capital. Out of a total profit of Rs.16500 at the end of the year, B's share is:
Answer: Rs.6000
Explanation:Let C = x.
Then B = 4x and 2A = 3 * 4x = 12x. or A = 6x.
Therefore, A : B : C = 6x : 4x : x = 6 : 4 : 1.
Therefore, B's capital = Rs. 16500 * 4/11= Rs.6000.
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3. The probability that a number selected at random from first 50 natural numbers is a composite number is
Answer: 17/25
Explanation:The number of exhaustive events = 50C1 = 50.
We have 15 primes from 1 to 50.
Number of favourable cases are 34.
Therefore, Required probability = 34/50 = 17/25.
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4. An article is sold at a certain price. By selling it at 2/3 of that price one loses 10%. Find the gain percent at original price.
Answer: 35%
Explanation:Let the original S.P be Rs. X.
Then new S.P = Rs. (2/3)X, Loss =10%
So, C.P = Rs. [100/90 * (2/3)X ] = 20X/27.
Now C.P = Rs. 20X/27, S.P =Rs. X.
Gain = Rs. [ X -20X/27 ] =Rs.7X/27.
Hence, Gain % = [ 7X/27 *27/20X *100 ]% = 35%.
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5. A lent Rs. 5000 to B for 2 years and Rs. 3000 to C for 4 years on simple interest at the same rate of interest and received Rs. 2200 in all from both of them as interest. The rate of interest per annum is:
Answer: 10%
Explanation:Let the rate be R% p.a.
Then, (5000 x R x 2)/100 + (3000 x R x 4)/100 = 2200.
=> 100R + 120R = 2200
=> R = 2200/220 = 10.
.'. Rate = 10%.
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6. In a group of donkeys and pigs, the numbers of legs are 16 more than twice the number of heads. The number of donkeys is
Answer: 8
Explanation:Let the number of donkeys be x and the number of pigs be y.
Then,
=> 4x + 2y = 2(x + y) = 16.
=> 2x + (2x + 2y) = (2x + 2y) + 16.
=> x = 8.
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7. The average age of five girls 11.The oldest among them is 15 years old.What is the average of the others?
Answer: 10
Explanation:Let 'T' be the total age of 5 girls.
Then, T/5 = 11.
=> T = 55.
Given, Age of the Oldest girl = 15.
Then, Total age of other 4 girls will be 55-15=40.
So, Avg. of other 4 girls 40/4 = 10.
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8. What must be added to the two numbers, which are in ratio 5 : 12, so that the new ratio becomes 3:4?
Answer: 16
Explanation:Let x be the required number.
Then, According to the question,
=> (5+x)/(12+x) = 3/4
=> 20 + 4x = 36 + 3x.
=> x = 16.
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9. Today, the age of a father is thrice the age of his son. Ater 5 years the age of father will be 2.5 times the age of his son. What is the age of son today?
Answer: 15 years
Explanation:Let the age of son = S years and the age of father = F years.
According to the question,
=> F = 3*S.
=> F = 3S.
After 5 years,
=> (F+5) = 2.5 * (S+5).
=> 3S + 5 = 2.5S + 12.5 [put F=3S]
=> 0.5S = 7.5
=> S = 15
Hence, the age of son = 15 years.
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10. A number lying between 1000 and 2000 is such that on division by 2, 3, 4,5,6,7 and 8 Leavers remainders 1, 2, 3, 4, 5,6and 7 respectively. The number is
Answer: 1679
Explanation:LCM(2,3,4,5,6,7,8)= 1680
2-1=3-2=4-3=...=8-7=1
So, the number = 1680-1 = 1679
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