Thread: Stumped

Please forgive me if I have this in the wrong forum, but I am 'stuck' my 12yr old daughter came to me with this & I want to run & hide..

Avg. of 4#'s is 27
Avg. of 3#'s is 31
What is the 4th #?

Any help seriously appreciated

Originally Posted by alpina17

Please forgive me if I have this in the wrong forum, but I am 'stuck' my 12yr old daughter came to me with this & I want to run & hide..

Avg. of 4#'s is 27
Avg. of 3#'s is 31
What is the 4th #?

Any help seriously appreciated

Dear alpina17,

I don't quite understand your question. What do you mean by "Avg. of 4#'s". Is it average of four numbers in a series?

call your 4 numbers:

the average of these numbers is

but you have the answer to this

i.e.

=> multiplying across by the you get:

if it's the same set of numbers,

then the average of these is



you also have the answer to this

i.e.

=> multiplying across by the you get:

so therefore must be:

Excellent! believe it or not that's what I did; 108 - 93
but being honest I had no idea why I was submitting 15,
Now that you have explained, thank you very very much
maybe my daughter will not look at me as a 'd'oh...(well probably asking too much there!)