Questions

It is ABACUS.

Words formed are as below 

BUS
CAB
CUB
US

From the given data, 

if 60% = 45 minutes

100% =  ?

=> 45 × 100/60

= 75 min

i.e, = 1hr 15 min.

Concave type of glasses are used in the headlights of the vehicles as the light from the bulb which is at focus will converges out and spreads and reflects back parallely.

RADAR - RAdio Detection And Ranging.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. 

Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

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