1. In a class, the average score of girls in an examination is 73 and that of boys is 71. The average score for the whole class is 71.8. Find the percentage of girls.
(a) 40%
(b) 50%
(c) 55%
(d) 60%
Ans.(a)
Sol. Let the number of boys be x and that of girls be y
According to the question,
71x + 73y = 71.8(x + y)
⇒ 71.8x - 71x = 73y - 71.8y
⇒ 0.8x = 1.2y
⇒ x/y=1.2/0.8=12/8=3/2
Hence, percentage of gives =2/5×100
= 20 × 2 = 40%
2. If 24-carat gold is considered to be hundred percent pure gold, then the percentage of pure gold in 22-carat gold is..
(a) 91 (3/4)
(b) 91 (2/3)
(c) 91 (1/3)
(d) 90 (2/3)
Ans.(b)
Sol. Given, 24-carat gold = 100%
∴ 1-carat gold =100/24
∴ 22-carat gold =100/24×22
=2200/24
=91 (2/3)%
3. The ratio of the number of boys and girls in a school is 3 : 2. If 20% of the boys are 25% of the girls are scholarship holders, then the percentage of the students, who do not get the scholarship, is
(a) 78
(b) 75
(c) 60
(d) 55
Ans.(a)
Sol. Let - Boys = 300
Girls = 200
Boys and Girls who do not get the scholarship
300×80/100+200×75/100
240 + 150 = 390
%=390/500×100
= 78%
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