Question Detail

In the series 3, 9, 15.. what will be the 21st term ?

Answer: Option A

Explanation:

We can judge that it is A.P.
With 6 as difference
nth term in A.P. = a+(n-1)d
a= 3, n = 21, d = 6
So, 21st term will be = 3+(20)6 = 123

1. Complete the series 95, 115.5, 138, ..., 189

160.5
162.5
164.5
166.5

Answer: Option B

Explanation:

Pattern in the series is, +20.5 , +22.5,
Next will be +24.5
138 + 24.5 = 162.5

2. 1, 2, 5, 12, 27, 58, 121, ?

Answer: Option A

Explanation:

Pattern in the series is *2+1, *2+2, *2+3,.....

Term which replaces the question mark in the series is
121 * 2 + 6 = 248

3. 21,25,33,49,81, ?

Answer: Option B

Explanation:

Pattern is, +4, +8, +16, +32, so next will be +64
81+64 = 145

4. 1,1,3,9,6,36,10,100,(..),225

Answer: Option D

Explanation:

Given sequence is combination of two series
Series 1 : 1,3,6,10,..
Series 2 : 1,9,36,100,225

In series 1 pattern is +2, +3, +4. So next term will be
10+5 = 15

5. 1,6,15,(...),45,66,91

Answer: Option B

Explanation:

Pattern in the series is, +5, +9, .., .., +21, +25
So 4 is getting increased at every term addition.
Missing term in the series will be 15+(9+4)
= 15+13 = 28