What is the length of the diagonal in the parallelepiped with dimensions 11, 8 and 6 units of length.
- 13.5 units
- 14.8 units
- 10.3 units
- 19.5 units
- 25.3 units
The Usual Method
The length of the diagonal of the parallelepiped is given by:
Estimated Time to arrive at the answer = 45 seconds because of taking a square root of a non perfect square number.
Using some fundamental concepts of geometry as shown below:
The diagonal cannot be larger than the sum of all the three sides: 11 + 8 + 6 = 25 < 25.3. This eliminates option ‘5’.
Find the pairs of sums of length of sides as follows: 11 + 8 =19, 11 + 6 = 17 and 8 + 6 = 14. The answer has to lie between the largest sum and the smallest sum. i.e. between 19 and 14. This leaves us only with option ‘2’ as the answer.
Estimated Time to arrive at the answer = 10 seconds.