Percentage

Question: Two numbers A and B are such that the sum of 5% of A and 4% of B is two-third of the sum of 6% of A and 8% of B. Find the ratio of A : B.
[A].

2 : 3

[B].

1 : 1

[C].

3 : 4

[D].

4 : 3

Answer: Option D

Explanation:

5% of A + 4% of B =	2	(6% of A + 8% of B)
	3

	5	A +	4	B	=	2		6	A +	8	B
	100		100			3		100		100

	1	A +	1	B	=	1	A +	4	B
	20		25			25		75

		1	–	1	A =		4	–	1	B
		20		25			75		25

	1	A =	1	B
	100		75

A	=	100	=	4	.
B		75		3

Required ratio = 4 : 3

Video Explanation: YouTube Video

Question: What percentage of numbers from 1 to 70 have 1 or 9 in the unit’s digit?
[A].

1

[B].

14

[C].

20

[D].

21

Answer: Option C

Explanation:

Clearly, the numbers which have 1 or 9 in the unit’s digit, have squares that end in the digit 1. Such numbers from 1 to 70 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.

Number of such number =14

Required percentage =		14	x 100	% = 20%.
		70

Video Explanation: https://youtu.be/cBamI6iRNIA

Question: Rajeev buys good worth Rs. 6650. He gets a rebate of 6% on it. After getting the rebate, he pays sales tax @ 10%. Find the amount he will have to pay for the goods.
[A].

Rs. 6876.10

[B].

Rs. 6999.20

[C].

Rs. 6654

[D].

Rs. 7000

Answer: Option A

Explanation:

Rebate = 6% of Rs. 6650 = Rs.		6	x 6650		= Rs. 399.
		100

Sales tax = 10% of Rs. (6650 – 399) = Rs.		10	x 6251		= Rs. 625.10
		100

Final amount = Rs. (6251 + 625.10) = Rs. 6876.10

Video Explanation: https://youtu.be/XuiggCTh3SU