37. Rakesh credits 15% of his salary in his fixed deposit account and spends 30% of the remaining amount on groceries. If the cash in hand is Rs.2380, what is his salary?
a. Rs.3500
b. Rs.4000
c. Rs.4500
d. Rs.5000

Answer: B

Explanation:
Let salary be Rs.x. Then,
x - 15% of x -30% of 85% of x = 2380
or x - $\displaystyle\frac{{15x}}{{100}} - \displaystyle\frac{{30 \times 85 \times x}}{{100 \times 100}} = 2380$
or 200x - 30x - 51x = $2380 \times 200$
or 119x = $2380 \times 200$ or x $\displaystyle\frac{{2380 \times 200}}{{119}} = 4000$

38. The income of a broker remains unchanged though the rate of commission is increased from 4% to 5%. The percentage of slump in business is :
a. 8%
b. 1%
c. 20%
d. 80%

Answer: C

Explanation:
Let the business value changes from x to y.
Then, 4% of x = 5% of y or $\displaystyle\frac{4}{{100}} \times x = \displaystyle\frac{5}{{100}}\times y$
or y = $\displaystyle\frac{4}{5}x$
Change in business = $\left( {x - \displaystyle\frac{4}{5}x} \right) = \displaystyle\frac{1}{5}x$
Percentage slump in business
= $\left( {\displaystyle\frac{1}{5}x \times \displaystyle\frac{1}{x} \times 100} \right)$%

39. The price of an article is cut by 10%. To restore it to the former value, the new price must be increased by
a. 10%
b. $9\displaystyle\frac{1}{{11}}$%
c. $11\displaystyle\frac{1}{9}$%
d. 11%

Answer: C

Explanation:
Let original price = Rs.100
Then, new price = Rs.90
Increase on Rs.90=Rs.100
Increase % = $\left( {\displaystyle\frac{{10}}{{90}} \times 100} \right)$% $ = 11\displaystyle\frac{1}{9}$ %

40. By how much is 30% of 80 greater than $\displaystyle\frac{4}{5}th$ of 25?
a. 2
b. 4
c. 10
d. 15

Answer: B

Explanation:
Let the business value changes from x to y.
It is $\left( {\displaystyle\frac{{30}}{{100}} \times 80 - \displaystyle\frac{4}{5} \times 25} \right) = (24 - 20) = 4$

41. 12.5% of 192 = 50% of ?
a. 48
b. 96
c. 24
d. None of these

Answer: C

Explanation:
Let 12.5% of 192 = 50% of x.
Then, $\displaystyle\frac{{12.5}}{{100}} \times 192 = \displaystyle\frac{{50}}{{100}} \times x$
Then, x = $\displaystyle\frac{{12.5 \times 192}}{{50}} = 48$