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 the expression for the time taken for (i) The outward journey (ii) the return Journey. If the return journey took 30 minutes less than the onward journey write down an equation in x and find its value.

Krishna Mangaraj · 18th Feb 2019 .

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 the expression for the time taken for

(i) The outward journey (ii) the return Journey. If the return journey took 30 minutes less than the onward journey write down an equation in x and find its value.

Liza Mohapatra · 18th Feb 2019 .

(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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