Question

3. The ratio of the present ages of two brothers is 4:5. After 10 years, the ratio of their ages would be 6: 7. Find the age of the elder brother after 15 years.
(1) 35 years
(2) 40 years
(3) 50 years
(4) 25 years​

Answer 1

Answer:

let the present age of two brother is x and y year

then x:y=4:5

x/y=4/5

x=4y/5

after 10 years,

(x+10)/(y+10)=6/7

7x+70=6y+60

7x-6y= -10

7.4y/5 -6y= -10

28 y-30y= -50

-2y= -50

y=25

so the present age of elder brother is 25 years

after 15 years the age of the elder brother is

(25+15)years=40years

Answer 2

Answer:

Let present age of small brother be 4x and bigger brother be 5x

After 10years, small brother age be 4x+10 and bigger brother age be 7x+10

According to question

4x+10/7x+10 = 6/7. (by doing cross multiplication

7(4x+10) = 6(7x+10)

28x+70 = 42x+60 after interchanging their place

28x-42x = 60-70

-14x = -10

x= -10/-14 = 5/7 answer