21. If Ram’s height is 10% more than Shyam’s height. By how much % is Shyam’s height less than that of Ram’s ?
Sol:
22. A labour works 50 hrs. per week and he earns Rs. 3600 as wages. If his per hour wage is increased by 40% and duration of work is reduced by \(16\frac{2}{3}\)%, find the % change in his income.
Sol:
40% = \(\frac{2}{5}\)
\(16\frac{2}{3}\)% = \(\frac{1}{6}\)
∴ required % = \(\frac{5}{{30}}\) × 100 = \(16\frac{2}{3}\)%
Here the first sentence of the question is irrelevant.
23. Tax imposed on an article is increased by 20% and its consumption is decreased by 20%. Find the % change in revenue from it.
Sol:
20% = \(\frac{1}{5}\)
24. In a library, 40% of the books are in English. 30% of the remaining are in French and 60% of the remaining are in Russian. The remaining 16800 books are in Hindi. What is the total number of bricks in the library.
Sol:
Let the total number of books in library = x
then \(x \times \frac{{(100 – 40)}}{{100}} \times \frac{{(100 – 30)}}{{100}} \times \frac{{(100 – 60)}}{{100}} = 16800\)
⟹ \(x \times \frac{{60}}{{100}} \times \frac{{70}}{{100}} \times \frac{{40}}{{100}} = 16800\)
∴ x = 100000 Answer
25. The ratio of the number of males to that of females in a village is 3 : 2. If 30% of males and 70% of females are educated then find the ratio of the number of persons educated to uneducated.
Sol:
Let total number of persons = 100
26. If one side of a rectangle is increased by 5% and the other side is increased by 20%. Find the percentage value of which the area changes.
Sol:
27. In an examination A got marks 20% less than B. B got marks 25% more than C. C got marks 20% less than D. If A got 320 marks out of 500 then how much marks D got ?
Sol:
28. The ratio of number of boys and girls in a college is 4 : 5. If 15% of the boys & 20% of the girls are scholarship holders. Find the percentage of the college students who are not scholarship holders.
Sol:
∴ % marks of D = \(\frac{{400}}{{500}} \times 100\) = 80% Answer
29. A cow an a bull costs Rs. 1000 and 800 respectively. If the price of the cow and that of the bull is increased by 10% and 20% respectively then find the total cost of the one dozen cow and one dozen bulls.
Sol:
30. After three successive equal % rise in the salary, the sum of Rs. 100 turned into 133 Rs. and 10 paise. Find the percentage rise in the salary.
(i). 10 (ii). 11 (iii). 14 (iv). 16
Sol:
% rise in salary = \(\frac{{133.1 – 100}}{{100}} \times 100\) = 33.1%
now take the help from options.
option (ii). ⟹
using formula \(x + y + \frac{{xy}}{{100}}\)
⟹ \(10 + 10 + \frac{{10 \times 10}}{{100}}\)
= 21%
again
\(21 + 10 + \frac{{21 \times 10}}{{100}}\)
= 31 + 2.1
= 33.1%
Hence (i). 10% is correct option Answer