# 10th cbse maths solution for exercise 4.1 part 3

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## 10th cbse maths solution for exercise 4.1 part 3

(iii)
Rohan's mother is 26 years older than him. The product of their ages
(in years) 3 years from now will be 360. We would like to find Rohan's
present age.

Solution:

Let "x" be Rohan's age

Let "x + 26" be Rohan's mother's age

Three years later Rohan and his mother ages will be x + 3 and x + 29 respectively

(x + 3) (x + 29) = 360

x² + 29 x + 3 x + 87 = 360

x² + 32 x + 87 - 360 = 0

x² + 32 x - 273 = 0

(iv)
A train travels a distance of 480 km at a uniform speed. If the speed
had been 8 km/hr less, then it would have taken 3 hours more to cover the
same distance. We need to find the speed of the train.

Solution:

Distance to be covered = 480 km

Speed of the train = x km/hr

Time = Distance/speed

Time taken by the train to cover 480 km distance in x km/hr = 480/x

Time taken by the train to cover 480 km distance in 8 km/hr less speed = 480/(x - 8)

3 = [480/x] - [480/(x - 8)]

3 = 480 [ (1/x) - (1/(x-8))]

3/480 = [(x - 8 - x)/(x(x - 8))]

1/160 = -8/(x² - 8 x)

(x² - 8 x) = -8 (160)

x² - 8 x + 1280 = 0

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