Question

can anyone pls tell me when do we cross multiply and when do we multiply 10 * 75 im really confused

Answer 1

You don't multiply liters of gasoline by distance.

They are directly proportional - the more gasoline you have the longer is the dictance you can go.

So it's cross multiply.

Another examlpe:

you are paid by hour for your work. The more hours you have worked, the more you are paid:

hours      payment

2 h            $36

5 h             x    

$x=\dfrac{5\cdot36}2=90$

You would multiply 10•70 if they were inversely poportional values

For example:

1. speed and time of ride by given distance {the greater the speed the less time you need for a ride}

speed          time

10 m/s          75 s

 8 m/s           x

$x=\dfrac{10\cdot75}{8}=93.75\,s$

2. price and kolos of apples - the higher the pice the less of kilos you can buy by given cash

price          kilos of apples

$2                8

$4                x

$x=\dfrac{2\cdot8}{4}=4\,kg$