121. In an examination, 80% students passed in Hindi, 70% in English while 15% failed in both the subjects. If 455 students passed in both the subjects, then find the total number of students who appeared in the examination ?
Sol:-
122. After receiving two successive raises, Ankit’s salary became equal to \(\frac{{15}}{8}\) times of his initial salary. By how much % was the salary raised first time if the second time it was raised twice as high as the first.
Sol:-
overall ↑ in salary = \(\left( {\frac{{15}}{8} – 1} \right) \times 100\) = \(\frac{{700}}{8}\% \)
Let first ↑ = x%
∴ second ↑ = 2x%
⟹ \(\frac{{700}}{8}\) = x + 2x + \(\frac{{x \times 2x}}{{100}}\)
⟹ x² + 150x – 4375 = 0
x² + 175x – 25x – 43750 = 0
∴ x = 25% Answer
123. A spends 30% of his salary on house rent, 30% of the rest on items of daily use and 24% of the total salary he spends on children’s education. After his expenditure, he is left with Rs. 2500. What is salary of A ?
Sol:-
Let initial salary of A = 100 unit
∴ expense on houe rent = 30 ⟶ remaining = 70
expense on item of daily use = 21
& expense on children’s education = 100 × \(\frac{{24}}{{100}}\) = 24
total expense = 30 + 21 + 24 = 75
∴ saving = 100 – 75 = 25 unit ⟶ 2500
1 unit ⟶ 100
∴ salary of A = 100 × 100 = 10000 Answer
124. During winters, A can run ‘y’ meters on one bottle of glucose. But in the summer, he can run only ‘0.5y’ meters on one bottle of glucose. Then how many bottle of glucose are required to run 1000 meters during summer ?
Sol:-
During summer 0.5 meters ⟶ 1 bottle glucose
∴ 1 meter = \(\frac{1}{{0.5y}}\) bottle of glucose
∴ 1000 meters = 1000 × \(\frac{1}{{0.5y}}\)
= \( \boldsymbol{\frac{{2000}}{y}} \) Answer
125. A’s monthly salary is x rupees. Of this he spends y rupees. The next month he has an ↑ of z% in his salary and p% on his expenditure. Then what will be the new amount saved.
Sol:-
Saving = Income – Expenditure
∴ new amount saved = \( \boldsymbol{x\left( {1 + \frac{z}{{100}}} \right) – y\left( {1 + \frac{p}{{100}}} \right)} \) Answer
126. The ticket price in a cinema worth Rs. 160. When the price of the ticket lowered, the sale of the ticket ↑ by 50% while the collection recorded a decrease of 17.5%. Find the deduction in the ticket price.
Sol:-
127. The population of a city depreciates each year at the rate of 10% of its previous year value. However, every second year it depreciate at the rate of 5% of its previous value. If at the end of fourth year, the population of the village is 204687. Then find the population at the start of first year.
Sol:-
∴ required value = 40000 × 7
= 280000 Answer
128. In a school 70% of the students are boys & the rest are girls. Further \( \boldsymbol{12\frac{6}{7}} \)% of the boys and 10% of girls are getting a fee waiver. If the number of those getting a fee waiver is 90, find the total number of students getting 50% concession if it is given that 50% of those not getting a fee waiver are eligible to get half fee concession ?
Sol:-
total number of students not getting fee waiver = 100 – 12 = 88
∴ total number of students getting 50% concession = \(88 \times \frac{{90}}{{12}} \times \frac{1}{2}\) = 330 Answer
129. Out of the total procuction of copper from chalcopyrite, an ore of copper, 30% of the ore gets wasted, and out of the remaining ore, only 10% is pure copper. If the pure copper obtained in a year from a mine of chalcopyrite was 70000 kg, then the quantity of chalcopyrite mined from that mine in that year will be how much ?
Sol:-
∴ quantity of calcopyrite mined = 100 × 10000
= 1000000 kg Answer
130. A man buys a taxi for Rs. 350000. The annual repair cost comes to 3% of the price of purchase. Besides he has to pay an annual tax of Rs. 5000. At what monthly rent must he rent out the taxi to get a return of 20% on his net investment of the first year.
Sol:-
Net investment = 350000 + 350000 × \(\frac{3}{{100}}\) + 5000
= 365500
To get a return of 20% annualy, he must earn 365500 × \(\frac{{20}}{{100}}\) = 73100 Rs. annualy
∴ monthly rent = \(\frac{{73100}}{{12}}\) = 6091.67 Rs. Answer