The use of the word 'change' indicates that the obtained figure is compared against is the original weight. Change is 'difference' so we have:
color(blue)("difference is 137 - 124 = 13 tons.")
color(brown)("Always remember to use the units of measurement.") It is good practice, gains you marks and becomes very important when dealing with more complex calculations.
We need to compare this against something so we use the original weight. That is, a proportion of the original weight expressed as
color(white)(xxxxxxxx )13/124. This is 13 for 124 parts!
color(green)(.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~)
color(blue)("I am now going to show you something really cool!!!")
But this is a ratio comparing to 124 parts. We need the ratio compared to 100 parts. So I am now going to show you color(red)("why") people say multiply by 100. color(brown)("A number of people will only know this as a shortcut without")
color(brown)("fully understanding what it is actually doing.")
If we do this: " "(13 divide 124)/(124 divide 124) = (0.1048387....)/1 "for 1 part"
That is:color(white)(xxxxxxxxxxxx)(0.1048387..."parts".)/(1 " part")
But we need 'for 100 parts. So we now do this:
(0.1048387....times 100)/(1 times 100) = (10.48387..)/100 =10.58387 %
which is to 5 decimal places ( 5dp).
color(green)(.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~)
color(red)("Shortcut method")
color(red)( 13/124 times 100 = 10.584 %color(white)(xxxx) to 3dp
