General Mathematics

Question: If a sum of money at simple interest in `6`years,it will become `4` times in :
A
`12 years`

B
`14 years`

C
`16 years`

D
`18 years

Note: Let sum = x.Then,S.I.= x :. Rate`= ((100 xx x)/(x xx 6))%` `= 50/3%` Now, sum = x and S.I` = 3x`, Rate`= 50/3%` :. Time`= (100 xx 3x)/(x xx 50/3)` ` = 18 years`
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Question: If `a + b : b + c : c + a = 6 : 7 : 8` and `a + b + c = 14`, then the value of `c` is :
A
`6`

B
`7`

C
`8`

D
`14`

Note: Let `(a + b) = 6k`, `b + c = 7k` and `c + a = 8k`. Then,`2(a + b + c) = 21k` or `2 xx 14 = 21k` or `k = 4/3`. `:. a + b = (6 xx 4/3) = 8`. So, `c = (a + b + c) - (a + b)` `= (14 - 8)` `= 6`.
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Question: At a certain rate of simple interest a certain sum doubles itself in `10` years.It will treble itself in :
A
`12 years`

B
`15 years`

C
`20 years `

D
`30 years`

Note: Let sum = x.Then, S.I.= x .Time = `10` :. Rate`= ((100 xx x)/(x xx 10))%` `= 10%` Now, sum= x,S.I.= 2x, Rate`= 10%` :. Time`= (100 xx 2x)/(x xx 10) years` `= 20 years`.
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Question: A sum of money becomes`(8/5) of itself in `5`years at a certain rate of interest. The rate of interest is :
A
`5%`

B
`8%`

C
`10%`

D
`12%`

Note: Let sum = x.S.I. `= ((8x)/5 - x)` `= (3x)/5,Times = 5 years` :. Rate` = (100 xx (3x)/5 xx 1/(x xx 5))%` `= 12%`
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Question: The simple interest accrued of a sum of money at the end of four years is `1/5` of its principal. What is the rate of interest per annum ?
A
`4%`

B
`5%`

C
`6%`

D
Date inadequare

Note: Let sum = x.Then S.I `= x/5`, Times`= 4 `years :. Rate`= (100 xx x/5 xx 1/(x xx 4))%` `= 5%`
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Question: The simple interest on a sum of money at `8%` per annum for `6` years is half the sum. The sum is
A
`Rs. 4800`

B
`Rs. 6000`

C
`Rs. 8000`

D
Date inadequate

Note: Let sum = x. Then, S.I.`= x/2` `:. x/2 = (x xx 8 xx 6)/100`.Clearly,data is inadequate.
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Question: A sum of money trebles itself in `15` years `6` month. In how many years would it double itself ?
A
`6` years `3` month

B
`7` years `9` month

C
`8` years `3` month

D
`9` years `6` month

Note: Let sum = x. Then,S.I.`= 2x &`Time `= 31/2` years Rate` = ((100 xx 2x)/x xx 2/31)%` `= (400/31)%` :. Time` = ((100 xx x)/x xx 31/400)` years. `= 7` years`9` month
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Question: Simple interest on a certain sum at a certain rate is `9/16` of the sum. If the numbers representing rate percent and time in years be equal, then the rate is :
A
`5 1/2%`

B
`6 1/25`

C
`6 1/4%`

D
`7 1/2%`

Note: Let sum = x.Then, S.I.`= 9x/16`. Let time = n years & rate = n% `:. n = 100 xx (9x)/16 xx 1/x xx 1/n` `or n^2 = 900/16` `or n = 30/4` `= 7 1/2%`
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Question: The simple interest on a sum of money is `1/9` of the sum. The number of years is numerically equal to the rate percent per annum. The rate percent per annum is :
A
`3 1/3`

B
`5`

C
`6 2/3`

D
`10`

Note: Let sum = x.Then, S.I.`= x/9` Let time = n years and rate = n% Then, n`= 100 xx x/9 xx 1/(x xx n)` `or n^2 = 100/9` `or n = 10/3` `= 3 1/3%`
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Question: Consider the following ststements : If a sum of money is lent at simple interest, then the 1.money gets doubled in `5` years if the rate of interest is `16 2/3%` 2.money gets doubled four times if the rate of interest is `20%` 3.money becomes four times in `10`years if it gets doubled in `5` years. of these statements,
A
`1` and `3` are correct

B
`3` alone is correct

C
`2` alone is correct

D
`2` and `3` are correct

Note: Let sum be x.Then,S.I =x 1. Time`= (100 xx x)/(x xx 50/3)` `= 6` years (False) 2.Time `= (100 xx x)/(x xx 20)` `= 5`years (True) 3. Suppose sum = x. Then, S.I = x & Times `= 5` years Rate`= ((100 xx x)/(x xx 5))%` `= 20%` Now sum = x,S.I`.= 3x & Rate = 20%` :. Time` =((100 xx 3x)/(x xx 20))`years `= 15` years (false) So,`2` alone is correct.
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Question: If a sum of money at simple interest in `6`years,it will become `4` times in :

Question: If `a + b : b + c : c + a = 6 : 7 : 8` and `a + b + c = 14`, then the value of `c` is :

Question: At a certain rate of simple interest a certain sum doubles itself in `10` years.It will treble itself in :

Question: A sum of money becomes`(8/5) of itself in `5`years at a certain rate of interest. The rate of interest is :

Question: The simple interest accrued of a sum of money at the end of four years is `1/5` of its principal. What is the rate of interest per annum ?

Question: The simple interest on a sum of money at `8%` per annum for `6` years is half the sum. The sum is

Question: A sum of money trebles itself in `15` years `6` month. In how many years would it double itself ?

Question: Simple interest on a certain sum at a certain rate is `9/16` of the sum. If the numbers representing rate percent and time in years be equal, then the rate is :

Question: The simple interest on a sum of money is `1/9` of the sum. The number of years is numerically equal to the rate percent per annum. The rate percent per annum is :