Page 117 - Maths Skills - 8

Comparing Quantities 115

Present value of the machine at the start of second year = ` 60000 – ` 6000 = ` 54000

10
Decrease in value after further 1 year = 10% of ` 54000 = × ` 54000 = ` 5400
100
∴ Depreciated value after further 1 year, i.e., second year = ` (54000 – 5400) = ` 48600.

Example 10: When Tanushree left a city, the population was 9000. She recently heard that the population had
grown by 5%. What is the present population?
Solution: First, let us find the actual amount of the increase in population. Since the increase is 5 per cent of
the original, then the increase is:
5
5% of 9000 = 100 of 9000 = (0.05)(9000) = 450

The new population is the old population plus the increase in population, i.e.
9000 + 450 = 9450

Hence, the present population is 9450.

Exercise 8.1

1. Find p, if

(i) 5% of p is 20 (ii) 8.5% of p is 1.615
(iii) 3.5% of p is 42 (iv) 61% of p is 122
2. Convert

(i) 78% into a simple fraction (ii) 62% into a simple ratio
(iii) 13% into a decimal (iv) 125% into a simple ratio

3. Suresh’s income is 27% less than that of Mukesh. What per cent is Mukesh’s income more than that of
Suresh?

4. A’s income is 75% of the income of B. B’s income is 80% of the income of C. If A’s monthly income is
` 12900. Find the monthly incomes of B and C.
5. In a class-test, Arun secured 410 marks. If he secured 82% marks, find the maximum marks.

6. In an annual examination, Ravi got 85 marks in English, 70 in Hindi, 90 in Science, 98 in Maths,
75 in Sanskrit. Find the percentage of his aggregate marks if the maximum number of marks in each
subject was 100.

7. Sonia went to school for 260 days in a full year. If her attendance was 80%, find the number of days on
which the school was open.
8. Mrs. Saxena’s income is 23% more than Mrs. Sharma’s. What per cent is Mrs. Sharma’s income
less than Mrs. Saxena’s?
9. Alloys are mixture of metals. If an alloy of copper, zinc and nickel contains 72% copper, 24% zinc and
the rest nickel, find the mass of nickel in gram in 5 kg of the alloy.

10. A man’s income was ` 18000 per month. He spent 14% of his income on rent, and 54% on other things.
How much money did he save every month?