Question

An aeroplane travelled a distance of 400 km at an average speed of x km/hr. On the
return journey the speed was increased by 40 km/hr. Write down an expression for the
time taken for
[4]​

Answer 1

*Question:-

An aeroplane travelled a distance of 400 km at an average speed of x km/hr. On the

return journey the speed was increased by

40km/hr

Write down an expression for the

time taken for :-

*Answer:-

(i) Time taken for the onward journey = 400/x hours.

(ii) Time taken for the return journey =

400/x + 40 hours.

According to the question,

• ⇒ 400/x + 40 = 400/x – ½

• ⇒ 800x = 800(x + 40) – x(x + 40)

• ⇒ x2 + 40x – 32000 = 0

• ⇒ (x + 200)(x – 160) = 0

• ⇒ x = - 200 (inadmissible) or 160

Hence, the required value of x is 160.

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