Question

Lulu tells her little brother, Jack, that she is holding 20 coins all of which are dimes and quarters. They have a value of $4.10 . She says she will give him the coins if he can tell her how many of each she is holding.

Answer 1

q+d=20, d=20-q....

25q+10d=410, and using d from above in this equation gives you:

25q+10(20-q)=410

25q+200-10q=410

15q+200=410

15q=210

q=14, and since d=20-q

d=6

So Lulu has 14 quarters and 6 dimes.