51. If a man’s salary is 25% more than that of Naman, then how much percent is Naman’s salary less than that of
Aman ?
Sol:
∴ required % = \(\frac{{4 – 5}}{5} \times 100 = – 20\% \)
Hence Naman’s salary is 20% less than that of Aman. Answer
52. The price of rice rises by 20%. By how much percent should the consumption of rice be reduced so that the expenditure does not change.
Sol:
∴ required change in consumption = \(\frac{{5 – 6}}{6} \times 100\)
= –\( \boldsymbol{16\frac{2}{3}} \)%
i.e. consumption should be reduced by \( \boldsymbol{16\frac{2}{3}} \)% Answer
53. If the duty of an article is reduced by 60% of its present rate, By how much percent must its consumption increase in order that the revenue remain unaltered ?
Sol:
∴ required percent = \(\frac{{5 – 2}}{2} \times 100\) = 150% Answer
54. A number is first decreased by 20%. The decreased number is then increased by 20%. The resulting number is less than the original number by 40. Find the original number.
Sol:
Method(i):
net % change = 20 – 20 – \(\frac{{20 \times 20}}{{100}}\)
= -4% (i.e. 4% decrease) Answer
55. A number is first decreased by 20%. The decreased number is then increased by 20%. The resulting number is less than the original number by 40. Find the original number.
Sol:
56. If the price of an article is first decreased by 20% and then increased by 25%. Then find the net percentage change.
Sol:
57. If the price of an article is first increased by 20% and again increased by 10%. If the last increased price Rs. 198 then what was the original price.
Sol:
58. If the length, breadth and height of a cube are decreased, increased, increased by 5%, 10% and 20% respectively. Then what will be the impact on the volume of cube.
Sol:
59. While measuring the length of a rectangle it has been taken in 40% excess and its breadth was measured 40% less. Find the percentage change in its area.
Sol:
60. Ram saves 15% of his salary while Shyam saves 32%. If both get the same salary and Shyam saves 2240 Rs. then what is the saving of Ram ?
Sol:
Shyam’s saving 32% ⟶ 2240
1% ⟶ 70
∴ Shyam’s salary 100% ⟶ 100 × 70 = 7000
which is equal to Ram’s salary (Given)
∴ Ram’s salary = 7000
∴ Ram’s saving = 7000 × 15% = 1050 Answer