Question 752832
Formula for Mean (Average) = Sum of all numbers / Total number of numbers

<br />
Mean of 100 numbers = Sum of all hundred numbers / 100

<br />
We don't know the sum of all hundred numbers, so we call it x.

From the question, mean of 100 numbers is 45. Therefore:

{{{45=(x/100)}}}
Cross Multiply:
{{{4500=x}}}
Therefore, the sum of those hundred numbers is 4,500.

Now,
Mean of 99 numbers = Sum of all ninety-nine numbers / 99

We don't know the sum of all ninety-nine numbers, so we call it y.

Mean of 99 numbers is equal to 44 so,

{{{44=(y/99)}}}
Cross Multiply:
{{{4356=y}}}
Therefore, the sum of the remaining ninety-nine numbers is 4356.
<br />
Do you rememeber that when we had 100 numbers, the sum was 4,500?
When we removed one number, the sum became 4,356. So, what was that number we removed?

{{{4500-4356=144}}}
<br />
144 is the first number!