Quantitative Aptitude

Number Series

2,662 Questions
All First differences and arithmetic progressions 812 Successive multiplication or division 429 Step-wise calculations 349 Squares and cubes based 338 Separate alternate positions 241 Inter-term operations 144 Mixed-operation rules 138 Unconventional pattern solving 74 Fractional and decimal operations 60 Prime number based 54 Digit operations 23

Number Series Questions

Multiple choice

Find the nth term of the given sequence. 3, 6, 11, 18, 27, …

  1. n2 + 1

  2. n2 + 6n + 2

  3. n2 + 2

  4. n2 + 3n + 1
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The sequence is 3, 6, 11, 18, 27. The differences are 3, 5, 7, 9. This is a quadratic sequence. For n=1, n^2+2 = 3. For n=2, 2^2+2 = 6. For n=3, 3^2+2 = 11. The formula n^2+2 fits all terms.

Multiple choice

What of the following numbers is 25 less than the 25th term of the sequence 5, 9, 14, 20, ...?

  1. 352

  2. 377

  3. 394

  4. 382
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The sequence is 5, 9, 14, 20... Differences are 4, 5, 6... This is a quadratic sequence. n-th term = a + (n-1)d1 + (n-1)(n-2)d2/2. Here a=5, d1=4, d2=1. T_n = 5 + 4(n-1) + (n-1)(n-2)/2 = 5 + 4n - 4 + (n^2 - 3n + 2)/2 = (n^2 + 5n + 4)/2. For n=25, T_25 = (625 + 125 + 4)/2 = 754/2 = 377. 25 less than 377 is 352.

Multiple choice

Find the 20th term of the given sequence. 3, 5, 8, 12, ...

  1. 212

  2. 210

  3. 204

  4. 182
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The sequence is 3, 5, 8, 12. The differences are 2, 3, 4, which form an arithmetic progression. The n-th term is 3 + sum(i=1 to n-1 of (i+1)) = 3 + (n-1)(n+2)/2. For n=20, 3 + 19*22/2 = 3 + 209 = 212.