We know that Lance has one-dollar bills, and that the the bank gave 40 dimes for 4 one-dollar bills
4 one dollar bills = 4 dollars in total
Since he received 40 dimes for the money he had
⇒ 4 dollars = 40 dimes
⇒ 1 dollar = [tex]\frac{40}{4}[/tex] dimes
⇒ 1 dollar = 10 dimes
Hence, this implies that 1 dollar is equal to 10 dimes