# RS Aggarwal Class 7 Math Tenth Chapter Percentage Exercise 10B Solution

## EXERCISE 10B

**(1) Rupesh secures 495 marks out of 750 in his annual examination. Find the percentage of marks obtained by him.**

**(2) The monthly salary of a typist is Rs 15625. If he gets an increase of 12%, find his new salary.**

**(3) The excise duty on a certain item has been reduced to Rs 760 from Rs 950. Find the reduction per cent in the excise duty on that item.**

**(4) 96% of the cost of a TV is Rs 10464. What is its total cost?**

**(5) 70% of the students in a school are boys and the number of girls is 504. Find the number of boys in the school.**

Solution: Let the total number of student be x.

Percentage of boys = 70%

∴ Percentage of girls = (100 – 70)% = 30%

**(6) An ore contains 12% copper. How many kilograms of the ore are required to get 69 kg of copper?**

**(7) 36% of the maximum marks is required to pass a test. A student gets 123 marks and is declared fail by 39 marks. Find the maximum marks.**

**(8) A fruit-seller had some apples. He sells 40% of them and still has 420 apples. Find the number of apples he had originally.**

Solution: Let the required number of apples be x.

The percentage of sells apple = 40%

The percentage of rest apple = (100 – 40) = 60%

**(9) In an examination, 72% of total examinees passed. If the number of failures is 392, find the total number of examines.**

Solution: Let the total number of examines be x.

The percentage of passed examines = 72%

The percentage of failed examines = (100 – 72) = 28%

**(10) After deducting a commission of 5%, a moped costs Rs 15200. What is its gross value?**

Solution: Let the grass value be x.

Percentage of deducting commission = 5%

Percentage of mode commission = (100 – 5) = 95%

**(11) Gunpowder contains 75% of nitre and 10% sulphur, and the rest of it is charcoal. Find the amount of charcoal in 8 kg of gunpowder.**

Solution: Total amount of gunpowder = 8 kg = 8000 g

**(12) Chalk contains 3% of carbon, 10% of calcium and 12% of oxygen. Find the amount in grams of each of these substances in 1 kg of chalk.**

**(13) Sonal went to school for 219 days in full year. If her attendance is 75%, find the number of days on which the school was open.**

Solution: Let the number of days which the school was open be x.

**(14) 3% commission on the sale of a property amounts to Rs 42660. What is the total value of the property?**

Solution: Let the total value of property be x.

**(15) In an election, there were two candidates A and B. The total number of voters in this constituency was 60000 and 80% of the total votes were polled. If 60% of the polled votes were cast in favour of Ahow many votes were received by B?**

**(16) The price of a shirt is reduce by 12% in a discount sale. If its increased price is Rs 1188, find its original price.**

**(17) The price of a sweater is increased by 8%. If its increased price is Rs 1566, find the original price.**

**(18) After spending 80% of his income and giving 10% of the remainder in a charity, a man has Rs 46260 left with him. Find his income.**

**(19) A number is increased by 20% and increased number is decreased by 20%. Find the net increase or decrease per cent.**

**(20) The salary of an officer is increased by 20%. By what percentage should the new salary be reduce to restore the original salary?**

**(21) A property dealer charges commission at the rate 2% on the first Rs 2000000, 1% on the next Rs 200000 and 0.5% on the remaining price. Find his commission on the property that has been sold for Rs 540000.**

**(22) Nikhil’s income is 20% less than of Akhil. How much per cent is Akhil’s income more than that of Nikhil’s?**

**(23) John’s income is 20% more than that of Mr Thomas. How much per cent is the income of Mr Thomas less than that of Jhon?**

**(24) The value of a car decreases annually by 20%. If the present value is Rs 387000, what was its value 1 year ago?**

**(25) The value of car decreases annually by 20%. If the present value of the car be Rs 450000, what will be its value after 2 years?**

**(26) The population of a town increases 10% annually. If its present population is 60000, what will be population after 2 years?**

**(27) Due to an increase in the price of sugar by 25%, by how much per cent must a householder decrease the consumption of sugar so that there is no increase in the expenditure on sugar?**

Solution: Let the earlier consumption of sugar be 100 grams and let its price be Rs 100.

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