What number should be subtracted from both 31 and 40 so that their third proportional is 5 more than 43?

A. 1
B. 2
C. 4
D. 13

Answer

Correct Answer: C. 4

Solution

Let the number subtracted be T.

⇒ Third proportional of (31-T) and (40-T) is 5 more than 43.

⇒ (31 – T)/(40 – T) = (40 – T)/48

⇒ 1488 – 48T = 1600 + T2 – 80T

⇒ T2 – 32T + 112 = 0

⇒ (T – 28)(T – 4) = 0

∴ T can be either 28 or 4, but among the options only option 4 is given. So, 4 must be subtracted from both 31 and 40 so that their third proportional is 5 more than 43.

1/4 of Arif’s income and 1/3 of Babu’s income equal Tk. 1100.If 1/8 of Arif’s income is equal to 1/5 of babu’s income,what is Babu’s income?

A. 1100
B. 1200
C. 1400
D. 1500

Answer

Correct Answer: D. 1500

Solution

Ratio Of A:B=1/(1/8): 1/(1/5)=8:5

Now,1100 Tk. =((8x(1/4)+5x(1/3)) Part =11/3 part

Now,11/3 part =1100 Tk (According to the Question)
Then, B= 5 part= 1100x (3/11)x5=1500 Tk

Father’s present age is 50 yrs. His age was equal to his son’s present age at the time of the son’s birth. What was son’s age 10 yrs. ago?

A. 12
B. 15
C. 20
D. 25

Answer

Correct Answer: B. 15

Detail About MCQs

Let the son’s present age be x years.
From the given data, it is known that
Father’s age at the time of son’s birth = Son’s present age
∴ 50 – x =x
⇒ 50 = 2x
⇒ x = 25
∴ son’s age 10 yrs ago = (25 – 10) = 15 yrs.