Question

I need help with 21 please

Answer 1

when rounding up, decimals tend to lose accuracy, thus the rounding, due to that, fractions will always be the most accurate to represent the value, but let's go ahead

3/5 = 0.6 <- rounded up to one decimal

3/4 = 0.75

      = 0.8 <- rouned up to one decimal as well

if we add them up 0.6 + 0.8 = 1.4.

$\bf \cfrac{3}{5}+\implies \cfrac{3}{4}\implies \stackrel{\textit{using an LCD of 20}}{\cfrac{(4)3+(5)3}{20}}\implies \cfrac{12+15}{20}\implies \cfrac{27}{20} \\\\\\ 1.35\implies \stackrel{\textit{rounded up}}{1.4}$

in this case, rounding up each result to 1 decimal, we end up with the same value, mind you that the instructions never said to round it to a certain amount of decimal places, if we do round it to two decimal places, the value will be 1.35 for both cases, and accurate on each.