#1**+2 **

To do this question it is easier to work backwards from the qanswers.

Take the first answer.

\(\displaystyle\sum_{j=1}^7 \frac{1}{2}(j+1)\\ When\;\; j=1\quad \text{The first term is }\quad \frac{1}{2}(1+1)=1 \quad \text {that is good}\\ When \;\; j=2\quad \text{The second term is }\quad \frac{1}{2}(2+1)=\frac{3}{2}= \quad \text {that is no good}\\\)

So it is not the first one.

If you think about it, the bottom of the fractions are \(2^0,2^1,2^2,....\) and the top is just 1. So the bottom is a power of 2.

Which out of the 4 seems likely?

Test that one, like I tested the first one, and see if it works.

So what is the answer?

**Please no one answer over me.**

Melody Mar 21, 2019

#3**+1 **

Yes that becasue you need to think about my answer.

Not everything in life is instant!

Have you worked through how I looked at the first possibility and then dismissed it as wrong?

Melody
Mar 21, 2019