Aptitude - Odd Man Out and Series - Discussion

Except 81 is multiplied wit 9 & other numbers can be multiplied by itself.

All the numbers are prime numbers except 81.

Prime number series is 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997 etc.

3, 13, 31, 58, 91, 111 choose the wrong number in the series.

a) 58 b) 31 c) 91 d) 111.

Can anyone help me to solve this problem?

t = 41 + 2 * 1 = 43
t = 43 + 2 * 2 = 47
t = 47 + 2 * 3 = 53
t = 53 + 2 * 4 = 61
t = 61 + 2 * 5 = 71
t = 71 + 2 * 6 = 83.

In the given Series there 73 followed by 71, so the answer must be 73.

Answer 81 is correct. Because except 81, all other numbers are a prime number.

Yes, I agree with Sandeep Shenoy.

Why its ans can't be 47?

41 4>1
43 4>3
47 4<7
53 5>3
61 6>1
71 7>1
73 7>3
81 8>1

Every 10th digit no is more than except 47, so the answer is 47. Why this answer is wrong?

BUT why not 73 because its also not fit in series with 81? both are not fit isn't it?

If we solve like that:
43 - 41 = 2,
47 - 43 = 4,
53 - 47 = 6,
61 - 53 = 8,
71 - 61 = 10,
73 - 71 = 2.

So, that 73 makes an error for the exact difference between the given numbers so according to me, 73 is an answer .

It's 81.

That's because NO OTHER NUMBER IS PERFECTLY DIVISIBLE BY 3, EXCEPT 81.