Solution: (e)
\(\displaystyle {{13.5}^{2}}=182.25\approx 180\)
Alternately without pen and paper,
13 and 14 are the nearest numbers. Two times of 13 is 169 and 14 two times is 196. By elimination and approximation, we can see that the answer should lie in between these so, (e) is the answer.
13) \(\displaystyle 750.0003\div 19.999=?\)
(a) 49
(b) 18
(c) 22
(d) 45
(e) 38
Solution: (e)
\(\displaystyle ?=\frac{{750}}{{20}}=37.5\approx 38\)
Alternately without pen and paper,
750 divided by 10 is 75 and half of it is approximately 38. By approximation we can see that the answer should is, (e) is the answer.
Solution: (d)
\(\displaystyle \sqrt{{963}}+{{4.895}^{2}}-9.24=?\)
31 + 23.9 – 9.24 = ?
54.91 – 9.24 = ?
\(\displaystyle ?=45.6\approx 45\)
Alternate mind calculation,
30 two times is 900 so, 963 should be 31 or 32. So, take lower number 31. Now, 4.8 is approximately 5, two times of 5 is 25. So, 31+25 – 9 = 47. So, by approximation and elimination we see the answer is (d).
Solution: (e)
\(\displaystyle ?\approx 840\div 48\approx 17.5\)
Alternately without pen and paper
840 divided by 50 (nearest number to 48) is 16.8 or approximately 17. So, by elimination and approximation we see the answer as (e)
