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PAIRS OF EQUATIONSSTD 9

GENERAL OBJECTIVES To understand on equations To identify the pairs equations in the

given problem To solve problems by forming pairs of

equations

ACTIVITY 1Try to answer the following questions through mental

work 1. 5 books of the same prize and a pencil of Rs 5 were sold for

fifty five rupees. What is the prize of one book? ans : 2. Mini’s father and mother give some apple to her such that

mother give double as father give. Suppose mini got 21 apples in total. How much her father give to her?

ans : 3. Find the value of ‘x’ from the following equation 2x+y = 23 and y = 5 ans :

ACTIVITY 2Answer the following questions. You can do it in your

brain or you can use paper and pen for calculations.1. In a box there white and black balls. The number of black

balls is eight more than the number of white balls ; the total number of balls is four times the number of white balls. How many black and white balls are there in the box?

ans :

2. Four added to half of a number gives hundred. What is the number?

ans :

3. Two persons divided hundred rupees between them and one got ten rupees more than the other. How much did each get?

ans :

4. Raji’s age is three times that of her brother Rajan. After two years , Raji’s age would be two times that of Rajan. How old are they now?

ans :

5. A hundred rupee note was changed to ten rupee notes and twenty rupee notes, eight notes in all. How many tens and how many twenty notes are there?

ans :

ACTIVITY 3Read the following questions carefully and solve them 1. The number of girls in a class is 4 more than the number of

boys . On a day when only 8 boys were absent, the number of girls were double the number of boys. How many boys and girls are there in that class?

ans :

2. If 2 is added to the denominator of a fraction and the fraction is simplified, we get 1/4. If instead, 1 is added to the numerator and simplified, we get 2/5. what is the fraction?

ans :

3. The price of a table and a chair together is 2500 rupees. The price of 3 tables and 4 chairs of this kind is 8000 rupees. What is the price of each?

ans :

4. Thomas deposited 7000 rupees in all in two banks. The rate of interest is 8% in one bank and 11% in the other. After a year, he got 680 rupees as interest from both banks together. How much did he deposit in each bank?

ans :

5. Manu is 4 years younger than Mridula. 4 years back, Mridula’s age was one and a half times Manu’s age. What are their ages now?

ans :

ACTIVITY 4Try to answer the following problems as your own 1. The price of 2 pens and 3 notebooks is 29 rupees; for 2

pens and 5 notebooks, it is 43. what is the price of each? ans :

2. The price of 3 pencils and 4 pens is 26 rupees. The price of 6 pencils and 3 pens is 27 rupees. What is the price of each?

ans :

3. There are two cans, one large and one small. The small can filled five times and the large can filled two times together give 20 litres. The small can filled two times and the large can filled three times give only 19 litres. How much does each can contain?

ans :

4. Four times a number added to thrice another number gives 43. twice the second number, subtracted from thrice the first gives 11. what are the numbers?

ans :

5. Some autorikshaws and bikes are parked in a place. There are 19 in all. The total number of wheels is 45. how many of each vehicle are there?

ans :

6. The sum of digits of a two-digit number is 11. if the digits of the number are interchanged, we get a number which is 27 more than the original number. What is the number?

ans :

ANSWERS

ACTIVITY 11. 102. 73. 9

ACTIVITY 24. 4 white balls and 12 black balls5. 1926. 45, 557. Raji’s age = 6 Rajan’s age = 25. 6 ten rupee notes and 2 twenty rupee

notes

ANSWERSACTIVITY 3

1. 24 girls and 20 boys2. 3/103. Table’s price = Rs 2000 chair’s price = Rs 5004. He deposited Rs 3000 on the first and Rs

4000 on the other bank5. Manu’s age is 12 and Mridula’s age is 16

ANSWERS ACTIVITY 4

1. Rs 4 for a pen and Rs 7 for a notebook2. Rs 2 for a pencil and Rs 5 for a pen3. Small can contains 2 liter and large can

contains 5 liter4. First number is 7 and second number is 55. There are 7 autorikshaws and 12 bikes6. The number is 47

Prepared by Naseera P P

THE END