four times one and one half

This looks like:

$$4\times 1\frac{1}{2}$$

First, we have to turn one and one half into a improper fraction. We do this by multiplying the number before the fraction (here it is 1) and multiply that by the bottom number. Then, we add the top number to that. Finally, we put this number over the original bottom number. (which is 2 here)

$$4 \times \frac{1\times2+1}{2}$$

$$4\times\frac{2+1}{2}$$

$$4\times\frac{3}{2}$$

Now, 4 can really be written as 4/1, so now we get:

$$\frac{4}{1}\times\frac{3}{2}$$

And now we can multiply this like we would any two fractions. We just multiply the top numbers together. Then we multiply the bottom numbers together.

$$\frac{4\times3}{1\times2}$$

$$\frac{12}{2}$$

Reduce the fraction by dividing the top and bottom by 2.

$$\frac{6}{1}$$

Which is really:

$$6$$

Oops, I didn't notice the one and part! Nice, Ninja!