Fill in the missing number in the series.
3,10,7,8,--,12,9,16.
This is a discussion on Find Missing Number within the Brainteasers forums, part of the Brain Quiz category; Fill in the missing number in the series. 3,10,7,8,--,12,9,16....
Fill in the missing number in the series.
3,10,7,8,--,12,9,16.
hi,
the missing number is 7.
Sol 1.
3 10 7 8 -- 12 9 16
so, lets name them as
a=3, b=10, c=7, d=8, e=?, f=12, g=9, h= 16
a+9 gives you f(12), and b-1 gives you g(9), adn c+9 gives you h(16), so in that fashion d-1, should give you e, which will be 7 as the value of d=8.
Thanks
Sushma
3, 10, 7, 8
3*2, 10+2, 7+2, 8*2
6, 12, 9, 16
So the missing number is 6
The missing number is 5
Here is how i found out
There are two sequences interwined
one is a sequence of even numbers and another one is a sequence of odd numbers
Consider the odd numbers and take three numbers at a time
the lowest number is 3 and the first set of 3 odd numbers would be 3,5 and 7.
Write them in the order of 1st, third and second ie (o1,o3,o2) this will give 3,7 and 5.
Next set would be 9,13 and 11 and so on and so forth
Now consider the even number. each set has three numbers in the increasing order
The lowest numbers so far here is 8. Suppose the first set consists of (a1,a2,a3) then rewrite them by (a2,a1,a3). So a set (8,10,12) will become (10,8,12) followed by (16,14,18) and so on and so forth.
Now combine these two sequences odd one first and in between any two odd numbers insert the even numbers and the series would unravel
3,10,7,8,5,12,9,16,13,14,11,18,15,22,19,20,17,24....