Question

7. The sum of the present ages of Jamuna and Keerthi is 36 years and that of Jamuna and Lakshmi is 28 years. The ratio of Lakshmi's age and Keerthi's age is 2: 3. What is Keerthi's present age? (1) 22 years (2) 25 years (3) 20 years (4) 15 years (5) None of these​

Answer 1

Let Aman's son age =x

Aman's age =3x

Ten years ago, he was 5 times the age of his son.

Therefore, 3x−10=5(x−10)

3x−10=5x−50

2x=40

x=20

Aman's son is 20 yrs old

Aman is 3x=3×20=60 yrs old

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Answer 2

Step-by-step explanation:

Let age of Jamuna be x

Age of Keerthi be y

Age of Lakshmi be z

Given that,

x + y = 36 x + z = 28 z : y = 2 : 3

----(2) => 3z = 2y => y = 3z/2

Substitute value of y in 1St eqn.

x + 3z/2 = 36

2x + 3z = 36 × 2 = 72

2x + 3z = 72. -----(4)

Solve 2 and 4 by elimination method

2x + 3z = 72 2x + 3z = 72

2 ( x + z = 28 ). => 2x + 2z = 56

- - -

-----------------------

0 + z = 16

z = 16

Substitute value of z in y = 3z/2

y = 3 × 16 / 2

y = 24 years

Keerthi's present age is 24.

Summary of solution:

First find y in terms of z so that you can substitute it's value in any one eqn having x and y.

Then you will get two equations with two variables x and z, by solving those equations you can get the value of z and substitute it's value in any eqn having y as a variable ( bcz Keerthi's age was assumed as y )

Hope this helps you.

Have a nice day