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$ 21 is the true discount on $ 371 for a certain time at certain int. If the rate of interest is kept same, true discount on the same sum for double that time will be :
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- $ 44.38
- $ 39.75
- $ 33.25
- None of these
Correct Option: B
Given that , Amount = $ 371 , True discount = $ 21
∴ Present worth = Amount - True discount
Present worth = $ (371 - 21) = $ 350
Also, True discount = Simple Interest on Present worth
∴ Simple Interest on $ 350 for a certain period at certain rate p.c. = $ 21.
∴ Simple Interest on $ 350 for double the period at same rate p.c. = $ 42.
∴ $ 42 is True discount on $ (350 + 42) = $ 392 for double the period.
∴ T.D. on $ 371 for double the period and same rate p.c.
| True discount = | 42 | x 371 = $ 39.75 |
| 392 |
