Question

On a trip from the United States to Canada, Isabella took d U.S. dollars. At the border she exchanged them all, receiving 10 Canadian dollars for every 7 U.S. dollars. After spending 60 Canadian dollars, she had d Canadian dollars left. What is the sum of the digits of d?

Answer 1

Answer:

5

Step-by-step explanation:

The exchange rate is 10 CAD = 7 USD

Which means:

10/7 CAD for EACH USD

So, d USD would be:

d * 10/7 = (10d)/7 CAD

This is what she has now, after exchange (in CAD).

She spends 60 and has "d" left, so finding d:

$\frac{10d}{7}-60=d\\\frac{10d-420}{7}=d\\10d-420=7d\\3d=420\\d=\frac{420}{3}\\d=140$

Hence, d = 140

The digits of d are 1, 4, and 0

The sum is:

1 + 4 + 0 = 5

The sum is 5