Question

In 2009, the total country A debit card purchases were $1.5 trillion, up 37% from 2008. What were the total country A debit card purchases in 2008?

In 2008, total country A debit card purchases were
trillion.
(Type an integer or decimal rounded to one decimal place as needed.)

Answer 1

well, the total was really "x", which oddly enough is the 100% for 2008.

We also know that in 2009 it went up by 37%, that means 100% + 37% or 137% for 2009, and we know that that tis 1.5 trillion or namely 1.5E12, so

`\begin{array}{ccll} amount&\%\\ \cline{1-2} x & 100\\ \underset{trillions}{1.5}& 137 \end{array} \implies \cfrac{x}{1.5}~~=~~\cfrac{100}{137}\implies 137x = 150 \\\\\\ x = \cfrac{150}{137}\implies x \approx 1.095\implies \underset{trillions}{x\approx 1.1}`