Problem Solving

M7MBA wrote:A certain country had a total annual expenditure of $1.2 x 10^12 last year. If the population of the country was 240 million last year, what was the per capita expenditure?

(A) $ 500
(B) $1,000
(C) $2,000
(D) $3,000
(E) $5,000

The OA is E.

Should I divide the total population by the total expenditure? Am I right?

Let's use a nice rule that says: (ab)/(cd) = (a/c)(b/d)

Per capita expenditure = (total expenditure of country)/(total population of country)
= (1.2 x 10^12)/(240 million)
= (1.2 x 10^12)/(240 x 10^6)
= (1.2 x 10^3 x 10^9)/(240 x 10^6)
= (1.2 x 10^3 x 10^9)/(240 x 10^6)
= (1200 x 10^9)/(240 x 10^6)
= (1200/240)(10^9/10^6)
= (5)(10^3)
= (5)(1000)
= 5000

Answer: E

M7MBA wrote:A certain country had a total annual expenditure of $1.2 x 10^12 last year. If the population of the country was 240 million last year, what was the per capita expenditure?

(A) $ 500
(B) $1,000
(C) $2,000
(D) $3,000
(E) $5,000

The OA is E.

Should I divide the total population by the total expenditure? Am I right?

The key to solving this problem is to accurately translate from what is being asked to a mathematical expression. We need to determine the "per capital expenditure". As an expression, this is:

(Total annual expenditure)/(Total population)= per capita expenditure

The easiest first step is to express 240 million as a number times a power of 10 since the other number is in this format.
240 million = 240,000,000

Since we have a 24 with 7 zeroes we can write this as:

24 x 10^7

Next, we should adjust 1.2 x 10^12 to make it a more usable number in our expression.

1.2 x 10^12 = 120 x 10^10

We now can solve:

(Total annual expenditure) / (Total population)

(120 x 10^10) / (24 x 10^7)

5 x 10^3

5 x 1,000 = 5,000

Answer: E