A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series. 5, 11, 24, 51, ? with explanation
Answers
Step-by-step explanation:
Quite literally, any answer you want it to be. How come? Because any formula that returns the 5 numbers listed can always have an additional expression tacked on that vanishes for the first 5 positions. For eg, if you add to the ‘formula’ you have in mind, the expression (n-1)(n-2)(n-3)(n-4)(n-5)E where E is just about any expression you can think of (eg: PI, or PI/sqrt(2), or sin(n), and so on), you will definitely get 5, 11, 24, 51, 106. However in place of 217 you would produce something else!
Try this: existing formula + (n-1)(n-2)(n-3)(n-4)(n-5)
For n=1,…,5 this would return 5,11,24,51,106. However for n=6 you would get 217 + 6.5.4.3.2.1 = 217 + 720 = 937. How about if I wrote existing formula - (minus) the same expression, then the answer would be 217 - 720 = -503. Yet again, if it were the above expression * PI, the 6th term would be 217 + 720 times PI.
Such questions ought never to be asked in Math aptitude tests for this reason, and yet you come across this one in every Math test.