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An aeroplane leaves an airport and flies due North at 300 km/h. At the same time, another plane leaves the same airport and flies due West at 400 km/h. After 90 minutes, the distance between the two planes would be:

  1. 1000 km

  2. 900 km

  3. 800 km

  4. 750 km

Pythagoras Theorem

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Answer

An aeroplane leaves an airport and flies due North at 300 km/h. At the same time, another plane leaves the same airport and flies due West at 400 km/h. After 90 minutes, the distance between the two planes would be: Pythagoras Theorem, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

Let aeroplane flying in north direction at 300 km/h be at point P after 1.5 hours and aeroplane flying in west direction at 400 km/h be at point Q after 1.5 hours.

Given, 90 minutes = 1.5 hours

Speed of aeroplane P = 300 km/h

As we know,

Distance traveled = Speed × Time taken

AP = 300 × 1.5 = 450 km.

Speed of aeroplane Q = 400 km/h

As we know,

Distance traveled = Speed × Time taken

AQ = 400 × 1.5 = 600 km.

From figure,

Let ∠A = 90°

By Pythagoras theorem,

Hypotenuse2 = Perpendicular2 + Base2

In triangle APQ,

⇒ PQ2 = AP2 + AQ2

⇒ PQ2 = 4502 + 6002

⇒ PQ2 = 202500 + 360000

⇒ PQ2 = 562500

⇒ PQ = 562500\sqrt{562500}

⇒ PQ = 750 km.

Hence, Option 4 is the correct option.

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