Question

pls anyone answer this question......

Answer 1

Let the usual speed of plane be a km/h

Distance to be travelled = 1500 km

Time taken to travel with usual speed = 1500 / a hours

T1 = 1500 / a

Time taken to travel with new speed = 1500 / (a+100) hours

T2 = 1500 / (a+100)

According to question,

T1 - T2 = 30 / 60 hours


=> 1500 /a - 1500 /(a+100) = 1/2

=> 1500 ( 1 /a - 1 / a+100) = 1/2

=> 1500 ( a + 100 - a) / (a) (a+100) = 1/2

=> 1500 × 100 / ( a^2 + 100a) = 1/2

=> a^2 + 100a = 1500 × 100 × 2

=> a^2 + 100a = 300000

=> a^2 + 100a - 300000 = 0

=> a^2 + 600a - 500a - 300000 = 0

=> a (a+600) - 500(a +600) = 0

=> (a - 500)(a +600) = 0

a = 500 and - 600

But speed can't be negative,

So,

a = 500

Usual speed of plane = 500 km/h

Answer 2

Let the usual speed of plane be a km/h

Distance to be travelled = 1500 km

Time taken to travel with usual speed = 1500 / a hours

T1 = 1500 / a

Time taken to travel with new speed = 1500 / (a+100) hours

T2 = 1500 / (a+100)

According to question,

T1 - T2 = 30 / 60 hours

=> 1500 /a - 1500 /(a+100) = 1/2

=> 1500 ( 1 /a - 1 / a+100) = 1/2

=> 1500 ( a + 100 - a) / (a) (a+100) = 1/2

=> 1500 × 100 / ( a^2 + 100a) = 1/2

=> a^2 + 100a = 1500 × 100 × 2

=> a^2 + 100a = 300000

=> a^2 + 100a - 300000 = 0

=> a^2 + 600a - 500a - 300000 = 0

=> a (a+600) - 500(a +600) = 0

=> (a - 500)(a +600) = 0

a = 500 and - 600

But speed can't be negative,

So,

a = 500

Usual speed of plane = 500 km/h

hope it helped ❤️