Q1. The average of the first 100 positive integers is:
(a) 100
(b) 51
(c) 50.5
(d) 49.5
Sol.
The required average = (1+2+⋯……….. 100)/100
= (100 × 101)/(2 × 100) = 50.5
Q2. The average marks scored by Ganesh in English, Science, Mathematics and History is 15 marks less than what he scored in English, History, Geography and Mathematics. What is the difference of marks in Science and Geography, Ganesh scored?
(a) 40
(b) 50
(c) 60
(d) Data inadequate
Sol.
(E + S + M + H)/4-(E + H + G + M)/4 = 15
or, E + S + M + H – E – H – G – M = 60
∴ S – G = 60.
Q3. The average marks of 14 students was calculated as 71. But, it was later found that the marks of one student had been wrongly entered as 42 instead of 56 and of another as 74 instead of 32. The correct average is:
(a) 67
(b) 68
(c) 69
(d) 71
Sol.
Marks obtained by 14 students
= 14 × 71 = 994
Exact marks of 14 students
= 994 + {(56 – 42) + (32 – 74)}
= 994 + {14 + (–42)} = 994 + {–28}
= 994 – 28 = 966
∴ Correct average = 966/14 = 69.
Q4. Average weight of three boys P, T and R is 541/3 kg while the average weight of three boys T, F and G is 53 kg. What is the average weight of P, T, R, F and H?
(a) 53.8 kg
(b) 52.4 kg
(c) 53.2 kg
(d) Data inadequate
Sol.
We are to determine the average weight of P, T, R, F and H.
Obviously, this cannot be determined as we do not know the weight of H.
Q5. The average of four positive integers is 72.5. The highest integer is 117 and the lowest integer is 15. The difference between the remaining two integers is 12. Which is the higher of these two remaining integers?
(a) 73
(b) 84
(c) 70
(d) None of these
Sol.
We have, 117 + x + (x + 12) + 15 = 72.5 × 4
[where x is the lower integer among the remaining two integers]
⇒ 2x = 290 – 144
∴ x = 73
Hence the higher integer (among the remaining two integers)
= 73 + 12 = 85
Q6. The average weight of 8 persons increases by 1.5 kg. If a person weighting 65 kg is replaced by a new person, what could be the weight of the new person?
(a) 76 kg
(b) 77 kg
(c) 76.5 kg
(d) Data inadequate
Sol.
weight of the new person=8 × 1.5 +65=77kg
Q7. Kamya purchased an item for Rs. 46,000 and sold it at a loss of 12 percent. With that amount she purchased another item which he sold at a gain of 12%. What was her overall gain/loss?
(a) Loss of Rs. 662.40
(b) Profit of Rs. 662.40
(c) Loss of Rs. 642.80
(d) Profit of Rs. 642.80
Sol.
First S.P. = (46000 × 88)/100 = Rs. 40480
Second S.P. = (40480 × 112)/100 = Rs. 45337.6
∴ Loss = Rs. (46000 – 45337.6) = Rs. 662.4
Q8. A merchant purchases a wrist watch for Rs. 450 and fixes its list price in such a way that after allowing a discount of 10%, he earns a profit of 20%. Then the list price (in rupees) of the wrist watch is:
(a) Rs. 500
(b) Rs. 600
(c) Rs. 750
(d) Rs. 800
Sol.
Let, the list price of wrist watch be Rs. x.
Selling price of wrist watch at 10% discount
=Rs.x((100-10)/100)=Rs.9x/10
Cost price of wrist watch at 20% profit
= Rs. 9x/10 (100/(100 + 20)) = Rs. (9x/10×10/12) = Rs. 3x/4
Now, according to the question,
3x/4 = 450 ⇒ x = (450 × 4)/3 = 600
∴ List price of the wrist watch = Rs. 600
Q9. By selling an article for Rs. 21, a man lost such that the percentage loss was equal to the cost price. The cost price of the article was:
(a) Rs. 30 or Rs. 70
(b) Rs. 35 or Rs. 60
(c) Rs. 45
(d) R. 50
Sol.
Let, the cost of article be Rs. x. At x% loss, the article sold at Rs. 21.
Now, according to the question,
x((100-x)/100) = 21 ⇒ x(1-x/100) = 21
⇒ x-x^2/100 = 21 ⇒ x^2- 100x + 2100 = 0
⇒ (x – 30)(x – 70) = 0
∴ x = Rs. 30 or, Rs. 70
Q10. A sells an article to B at a gain of 25%, B sells it to C at a gain 20% and C sells it to D at a gain of 10%. If D pays Rs. 330 for it, how much did it cost A?
(a) Rs. 200
(b) Rs. 250
(c) Rs. 275
(d) Rs. 290
Sol.
Let, A buy the article in Rs. 100.
According to the question,
B’s cost = Rs. 125
C’s cost = Rs. 125((100 + 20)/100) = Rs. 150
D’s cost = Rs. 150((100 + 10)/100) = Rs. 165
Here, at the end the article was sold out at Rs. 165.
∴ Required cost for A = 330/165 × 100 = Rs. 200.
