Three odd numbers can not sum up to an even number.
15+15+ = 30
the original qiestion was
IUPAC exam question
Solve this.. ◻◻◻◻◻=30 Fill the boxes using (1, 3, 5, 7, 9, 11, 13, 15) U can also repeat the numbers..This question came in UPSC Final Exams held in Dec '13...... You will be glad to note that only Gaurav Agarwal could solve it.
The answer is +3+5+7+15 = 30
You have to have even number of odd numbers added to arrive at an even number.
The intended answer could be 7.5 + 7.5 + 15 = 30
or 3! + 9 + 15 or who knows what the UPSC wants. Hope the smart selected smart IAS officers can bring out the best in India.
There is a clever puzzle attributed to PAM Dirac (of Qunatum Mechanics fame)
https://stoove.wordpress.com/2012/04/15/dirac-ruined-everyones-fun/
This blog concludes with this gem!
So yeah, Dirac ruined the mathematicians fun, but I think the best thing about the anecdote is that he did it by showing them they were working on a trivial problem. That takes some *****.
Attempt Number 2 - This problem seems impossible as stated in post #2 in base 10 (decimal base), we change the base to 17
( normal base we use is 10 - as we have ten fingers - but UPSC people being super brainy people may have 17 fingers!)
15 + 15 +7 in base 17 becomes in decimal 22+22+7 = 51 which is 30 in base 17.
My previous answer 7.5 comes from 7 and 5 and two ink spots (.)
Entering forum after a break!Please use only 3 numbers from the above, not 4 .........
Entering forum after a break!
There is no way to have ONLY three numbers because all the numbers are odd
and three of them will NEVER give 30 as total! :nono:
I thought of 15 + 13 + (11 - 9) and many other combinations with one minus symbol.
Eg:
15 + 11 + (9 - 5)
15 + 9 + (7 - 1)
15 + 7 + (13 - 5)
15 + 5 + (11 - 1)
and so on...................
But............. Google search gave the BEST answer using all the numbers!
15 + 13 + (11-9)/(7-5)*(3-1) = 30
WOW! Brilliant !! :clap2:
Entering forum after a break!
There is no way to have ONLY three numbers because all the numbers are odd
and three of them will NEVER give 30 as total! :nono:
I thought of 15 + 13 + (11 - 9) and many other combinations with one minus symbol.
Eg:
15 + 11 + (9 - 5)
15 + 9 + (7 - 1)
15 + 7 + (13 - 5)
15 + 5 + (11 - 1)
and so on...................
But............. Google search gave the BEST answer using all the numbers!
15 + 13 + (11-9)/(7-5)*(3-1) = 30
WOW! Brilliant !! :clap2: