Question

plz help me...
I can't understand

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Answer 1

here is the answer . enjoy .

Answer 2

▁ ▂ ▄ ▅ ▆ ▇ █ SOLUTION █ ▇ ▆ ▅ ▄ ▂ ▁

let

• the usual speed of plane be X km/h
• the new speed of plane be X+250 km/h

According to the question

$↪ \frac{1500}{x} - \frac{1500}{x + 250} = \frac{30}{60} \\ \\ ↪ \frac{1500x + 375000 - 1500x}{x(x + 250)} = \frac{30}{60} \\ \\ ↪ \frac{375000}{ {x}^{2} + 250x } = \frac{1}{2} \\ \\ ↪ {x}^{2} + 250x = 750000 \\ \\ ↪ {x}^{2} + 250x - 750000 = 0 \\ \\ ↪ {x}^{2} + 1000x - 750x - 750000 = 0 \\ \\ ↪x(x + 1000) - 750(x + 100) = 0 \\ \\ ↪(x - 750)(x + 1000) = 0\\ \\ ↪x - 750 = 0 \\ ↪x = 750 \\ ↪x + 1000 = 0 \\ ↪x = - 1000$

here negative value can't be kept

hence:-

the usual speed of plane is 750km/h