SECTION D
Questions number 26 to 30 carry 6 marks each.
Q. 26. An aeroplane left 30 minutes later than its scheduled time; and in order to reach its destination 1500 km away in time, it has to increase its speed by 250 km/hour from its usual speed. Determine its usual speed.
Ans. 750 km/hr
See Q.18 (Or), 2005 (Comptt. I Outside India).
Q. 27. A person standing on the bank of a river observes that the angle of elevation of the top of a tower standing on the opposite bank is 60°. When
he moves 40 m away from the bank, he finds the angle of elevation to be 30°. Find the height of the tower and the width of the river. 
Sol. Let AB be the tower, C and D be the two points of observation.
Let BC = x m and AB = h m
In rt. ΔABC,
Or
As observed from the top of a lighthouse, 100 m high above sea level, the angle of depression of a ship sailing directly towards it, changes from 30°
to 60°. Determine the distance travelled by the ship during the period of observation. 
Sol.
Let AB be the lighthouse, C and D be the two points
| Mathematics 2008 Question Papers Class X | |||||||
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