A person has 20 coins, all nickels and dimes, worth one dollar and 40 cents. How many nickels are there?

If n = number of nickels and d = number of dimes, which system of equations represents the problem?
n + d = 20 and n + d = 1.40
n + d = 20 and 5n + 10d = 1.40
n + d = 20 and 5n + 10d = 140

Question

A person has 20 coins, all nickels and dimes, worth one dollar and 40 cents. How many nickels are there?

If n = number of nickels and d = number of dimes, which system of equations represents the problem?
n + d = 20 and n + d = 1.40
n + d = 20 and 5n + 10d = 1.40
n + d = 20 and 5n + 10d = 140

anonymous · Answer

i think theirs an answer choice missing, because where it says 5 and 10, its supposed to be .05 and .10

anonymous · Answer

?

anonymous · Answer

Clearly the first choice can't be true.  n+d can't be both 20 and 1.40.  

The second one is better, but suffers from a clash of units.  The second equation is set up in cents on the LHS, and dollars on the RHS.  That is a problem.  

The third option is better.  It is similar to the second, but is set up with the units (cents) the same on both sides of the equal sign.  That one is your winner.

anonymous · Answer

yeah AnimalAin is right, i just didn't think out side the box; lol