Quantitative Aptitude - Arithmetic Ability Questions

Given 311   230   294   ?   281   256

311 - (9x9) = 230

230 + (8x8) = 294

294 - (7x7) = 245

245 + (6x6) = 281

281 - (5x5) = 256

Hence, the missing number in the given series is 245.

The terms of the series are products of two consecutive prime numbers i.e.

(2 x 3), (3 x 5), (5 x 7), (7 x 11),.....

So, 165 is wrong and must be replaced by (11 x 13) i.e. 143.

Here given 

2, 3, 6, 15, ? , 157.5

2 x 1.5 = 3

3 x 2  = 6

6 x 2.5 = 15

15 x 3 = 45

45 x 3.5 = 157.5

Therefore, the missing number is 45

17th June, 1998 = (1997 years + Period from 1.1.1998 to 17.6.1998)
Odd days in 1600 years = 0
Odd days in 300 years = 1
97 years has 24 leap years + 73 ordinary years.
Number of odd days in 97 years ( 24 x 2 + 73) = 121 = 2 odd days.
Jan. Feb. March. April. May. June.
(31 + 28 + 31 + 30 + 31 + 17) = 168 days
168 days = 24 weeks = 0 odd day.
Total number of odd days = (0 + 1 + 2 + 0) = 3.
Given day is Wednesday.

$$\begin{gathered} ?2 = 2×78-21+8+49-148 \\ = 57 - 21 \\ =36 \\ => ? = ±6 \end{gathered}$$

Let the required number days be x.

Less spiders, More days (Indirect Proportion)

Less webs, Less days (Direct Proportion)

 Spiders1:7Webs7:1⋮⋮ 7:x 

=> 1 * 7 * x = 7 * 1 * 7 

=> x= 7

Total distance travelled in 12 hours    =(35+37+39+.....upto 12 terms)
This is an A.P with first term, a=35, number of terms,
n= 12,d=2.
Required distance    = 12/2[2 x 35+{12-1) x 2]
=6(70+23)
= 552 kms.