General Mathematics

Question: What will be`160%` of a number whose`200%` is `140 ?`
A
`200`

B
`160`

C
`140`

D
`112`

Note: Let`200% of x = 140.` Then,`200/100 xx x = 140` `or x = 70` Now,`160% of 70 = 160/100 xx 70` `= 112.`
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Question: If `75%` of a number is added to `75` the result is the number itself. Then the number is :
A
`400`

B
`300`

C
`60`

D
`50`

Note: `75% of x + 75` `= x ⇒ x - 75/100 x = 75` `:. x - (3)/(4) x = 75` `or x/4 = 75` `or x = 75 xx 4` `= 300`
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Question: Subtracting`40%` of a number from the number, we get the result as `30`. The number is :
A
`28`

B
`50`

C
`52`

D
`70`

Note: `x - 40%` of `x = 30 ⇒ x - (40)/(100) x` `= 30 ⇒ x - (2)/(5) x = 30` `:. (3x)/5 = 30` `or x = (30 xx 5/3)` `= 50.`
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Question: If three fifth of a number is `40` more than `40%` of the same number what is the number ?
A
`100`

B
`150`

C
`200`

D
`400`

Note: `(3)/(5) x - 40%` 0f` x - 40 ⇒ (3)/(5) x - (40)/(100) x` `= 40` `or (3)/(5) x - (2)/(5) x = 40` `or x/5 = 40` `or x = (40 xx 5)` `= 200.`
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Question: Gold is `19` times as heavy as water and copper is `9` times as heavy as water. In what ratio should these be mixed to get an alloy `15` times as heavy as water ?
A
`1 : 1`

B
`2 : 3`

C
`1 : 2`

D
`3 : 2`

Note: Let `1` gm of gold be mixed with `x` gm of copper to give `(1 + x)` gm of alloy. Now, `1 G = 19 W, 1C = 9W & Alloy = 15 W` `1` gm gold ` + x ` gm Copper `= (1 + x)`gm alloy. `:. 19 W + 9 Wx = (1 + x) xx 15W` or ` x = (4W)/(6W) = 2/3`. So, the ratio of gold and copper is `1 : 2/3` or `3 : 2`.
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Question: A number, on subtracting `15` from it, reduces to its `80%.` What is `40%` of that number ?
A
`60`

B
`45`

C
`30`

D
`90`

Note: `x - 15` `= (80)/(100) x ⇒ x - 15` `= (4)/(5) x ⇒ x - (4)/(5) x = 15` `:. x/5 = 15` `or x = (15 xx 5)` `= 75.` Now,`40%` of `75` `= (40/100 xx 75)` `= 30`
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Question: Calculation shows that an angle is `37 1°/2.` The size obtained by drawing and measurement is `36°`. The error percent is :
A
`1 1/2`

B
`3`

C
`4`

D
`4 1/6`

Note: Error on`37 1/2` `= (37 1/2 - 36)` `= 1 1/2`. :. Error on `75/2 = 3/2.` Error on`100 = (3/2 xx 2/75 xx 100)` `= 4%`
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Question: `85` kg of a mixture contains milk and water in the ratio `27 : 7`. How much more water is to be added to get a new mixture containing milk and water in the ratio `3 : 1` ?
A
`5` kg

B
`6.5` kg

C
`7.25` kg

D
`8` kg

Note: Milk in `85` kg `= (85 xx (27)/(34))` kg `= (135)/2` kg. Water in `85` kg `= (85 xx (135)/2)` kg `= (35)/2` kg. Let `x` kg of water be added. `(Milk)/(Water) = 3/1` `iff ((135)/2)/((35)/2 + x) = 3/1` or `(135)/(35 + 2x) = 3/1` or `6x + 105 = 135` or `x = 5` kg.
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Question: The population of a town has increased from `133575` to `138918`. The percent increase in population is
A
`2.5`

B
`3`

C
`3.5`

D
`4`

Note: Increase on` 133575` `= (138918 - 133575)` `= 5343` :. Increase on `100 = (5343/133575 xx 100)%` `= 4%`
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Question: `15` litres of a mixture contains `20%` alcohol and the rest water. If `3` litres of water be mixed in it, the percentage of alcohol in the new mixture will be :
A
`15`

B
`16 2/3`

C
`17`

D
`18 1/2`

Note: Alcohol in `15` litres `= ((20)/(100) xx 15)` litres `= 3` litres. Percentage of alcohol in new mix. `= (3/(15 + 3) xx 100)%` `= 16 2/3 %`
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Question: What will be`160%` of a number whose`200%` is `140 ?`

Question: If `75%` of a number is added to `75` the result is the number itself. Then the number is :

Question: Subtracting`40%` of a number from the number, we get the result as `30`. The number is :

Question: If three fifth of a number is `40` more than `40%` of the same number what is the number ?

Question: Gold is `19` times as heavy as water and copper is `9` times as heavy as water. In what ratio should these be mixed to get an alloy `15` times as heavy as water ?

Question: A number, on subtracting `15` from it, reduces to its `80%.` What is `40%` of that number ?

Question: Calculation shows that an angle is `37 1°/2.` The size obtained by drawing and measurement is `36°`. The error percent is :

Question: `85` kg of a mixture contains milk and water in the ratio `27 : 7`. How much more water is to be added to get a new mixture containing milk and water in the ratio `3 : 1` ?

Question: The population of a town has increased from `133575` to `138918`. The percent increase in population is

Question: `15` litres of a mixture contains `20%` alcohol and the rest water. If `3` litres of water be mixed in it, the percentage of alcohol in the new mixture will be :