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11
Rs. 20 is the true discount on Rs. 260 due after a certain time. What will be the true discount on the same sum due after half of the former time, the rate of interest being the same?
Discuss
Answer & Solution
Answer: Option B
Solution:
S.I. on Rs. (260 - 20) for a given time = Rs. 20
S.I. on Rs. 240 for half time = Rs. 10
T.D. on Rs. 250 = Rs. 10
∴ T.D. on Rs. 260
= Rs. $$\frac{10}{250}$$  × 260
= Rs. 10.40
12
The interest on Rs. 750 for 2 years is the same as the true discount on Rs. 960 due 2 years hence. If the rate of interest is the same in both cases, it is:
Discuss
Answer & Solution
Answer: Option B
Solution:
S.I. on Rs. 750 = T.D. on Rs. 960
This means P.W. of Rs. 960 due 2 years hence is Rs. 750
∴ T.D. = Rs. (960 - 750) = Rs. 210
Thus, S.I. on R.s 750 for 2 years is Rs. 210
$$\eqalign{ & \therefore {\text{Rate}} = \left( {\frac{{100 \times 210}}{{750 \times 2}}} \right)\% \cr & = 14\% \cr} $$
13
The simple interest and the true discount on a certain sum for a given time and at a given rate are Rs. 85 and Rs. 80 respectively. The sum is:
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & {\text{Sum}} = \frac{{S.I.\, \times\, T.D.}}{{ {S.I.} - {T.D.} }} \cr & = \frac{{85 \times 80}}{{ {85 - 80} }} \cr & = Rs.\,1360 \cr} $$
14
The present worth of Rs. 1404 due in two equal half-yearly installments at 8% per annum simple interest is:
Discuss
Answer & Solution
Answer: Option A
Solution:
Required sum
= P.W. of Rs. 702 due 6 months + P.W. of Rs. 702 due 1 year hence
$$\eqalign{ & = Rs.\,\left[ { {\frac{{100 \times 702}}{{100 + 8 \times \frac{1}{2}}}} + {\frac{{100 \times 702}}{{100 + \left( {8 \times 1} \right)}}} } \right] \cr & = Rs.\,\left( {675 + 650} \right) \cr & = Rs.\,1325 \cr} $$
15
If the true discount on s sum due 2 years hence at 14% per annum be Rs. 168, the sum due is:
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & P.W. = \frac{{100 \times T.D.}}{{R \times T}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{100 \times 168}}{{14 \times 2}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 600 \cr & \therefore {\text{Sum}} = \left( {P.W. + T.D.} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = Rs.\left( {600 + 168} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = Rs.\,768 \cr} $$
16
A tradesman marks his goods 10% above his cost price. If he allows his customers 10% discount on the marked price. How much profit or loss does he make, if any ?
Discuss
Answer & Solution
Answer: Option B
Solution:
Let cost price of goods = Rs 100
Market price of goods
$$\eqalign{ & = 110\% {\text{ of }}100{\text{ }} \cr & = \frac{{110}}{{100}} \times 100 \cr & {\text{ = Rs}}{\text{. 110}} \cr} $$
After discount selling price of goods
$$\eqalign{ & = 90\% {\text{ of }}110 \cr & = \frac{{90}}{{100}} \times 110 \cr & = {\text{Rs}}{\text{. 99}} \cr} $$
Loss = 100 - 99 = Rs. 1
$$\eqalign{ & {\text{Loss }}\% {\text{ = }}\frac{1}{{100}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 1\% \cr} $$

Alternate :
$$\eqalign{ & {\text{Loss}}\% {\text{ = }}\frac{{x \times y}}{{100}}\% \cr & {\text{Loss}}\% {\text{ = }}\frac{{10 \times 10}}{{100}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 1\% \cr} $$
17
A discount of $${\text{2}}\frac{1}{2}\% $$  is given to the customer on the marked price of an article. A man bought the article for Rs 39. The marked price of the article is = ?
Discuss
Answer & Solution
Answer: Option C
Solution:
Discount = 2.5%
\[ = \frac{{2.5}}{{100}} = \frac{1}{{40}}\begin{array}{*{20}{c}} { \to {\text{Discount}}} \\ {{\text{ }} \to {\text{Market Price}}} \end{array}\]
Market Price = Rs. 40
Discount = Rs. 1
Cost Price = 40 - 1 = Rs. 39
39 → 39 Actual Cost Price
40 → Rs. 40
18
The marked price of a watch was Rs. 720. A man bought the same for Rs. 550.80, after getting two successive discounts, the first 10%. What was the second discount rate ?
Discuss
Answer & Solution
Answer: Option C
Solution:
Market price of a watch = Rs. 720
After 1st discount
$$\eqalign{ & {\text{ = 90}}\% {\text{ of 720 }} \cr & {\text{ = }}\frac{{90}}{{100}} \times 720 \cr & = {\text{Rs}}{\text{. 648}} \cr} $$
Cost price of watch = Rs. 550.80
Difference
= 648 - 550.80
= Rs. 97.20
$$\eqalign{ & {{\text{2}}^{{\text{nd}}}}{\text{ discount}} \cr & = \frac{{97.20}}{{648}} \times 100 \cr & = \frac{{9720}}{{648}} \cr & = 15\% \cr} $$
19
A shopkeeper marks his goods 20% above cost price, but allows 30% discount for cash payment. His net loss is ?
Discuss
Answer & Solution
Answer: Option C
Solution:
Let the cost price of goods = Rs. 100
Market price of goods
$$\eqalign{ & {\text{ = 120}}\% {\text{ of 100 }} \cr & {\text{ = }}\frac{{120}}{{100}} \times {\text{100}} \cr & {\text{ = Rs}}{\text{. 120}} \cr} $$
After discount selling price of goods
= 70% of 120
= Rs. 84
$$\eqalign{ & {\text{Loss = 100}} - 84 = {\text{Rs}}{\text{.16}} \cr & {\text{Loss }}\% {\text{ = }}\frac{{16}}{{100}} \times 100 = 16\% \cr} $$

Alternate :
$$\eqalign{ & {\text{Formula = }}x \pm y \pm {\text{ }}\frac{{x \times y}}{{100}} \cr & {\text{Loss}}\% {\text{ = 20}} - {\text{30}} - \frac{{20 \times 30}}{{100}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = - 10 - 6 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = - 16\% {\text{ }}({\text{Loss)}} \cr} $$
20
The equivalent single discount for two successive discounts of 15% and 10% is = ?
Discuss
Answer & Solution
Answer: Option C
Solution:
Equivalent to a single discount
$$\eqalign{ & = 15 + 10 - \frac{{15 \times 10}}{{100}} \cr & = 25 - 1.5 \cr & = 23.5\% \cr} $$

Alternate :
$$\eqalign{ & {\text{Market price = Rs}}{\text{.100}} \cr & {\text{Cost price}} \cr & {\text{ = 100}} \times \frac{{85}}{{100}} \times \frac{{90}}{{100}} \cr & {\text{ = Rs}}{\text{. }}76.5 \cr & {\text{Difference = 100}} - 76.5 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 23.5 \cr & {\text{Difference}}\% \cr & = \frac{{23.5}}{{100}} \times 100 \cr & = 23.5\% \cr} $$