Money and algebra

[robert marshall]

Todd has $75 and Bob has $90. Both boys have the same number of bills. If the boys only have $5 bills and $10 bills and Todd has the same number of $5 bills as Bob has $10 bills, how many $5 bills dos Todd have?

 

[Deleted member 4993]

Todd has $75 and Bob has $90. Both boys have the same number of bills. If the boys only have $5 bills and $10 bills and Todd has the same number of $5 bills as Bob has $10 bills, how many $5 bills dos Todd have?

Start with naming things to be found (unknowns):

Let

Number five dollar bills with Todd = F_T

Number Ten dollar bills with Todd = T_T

then we know: Todd has $75

so:

5*F_T + 10*T_T = 75..................................................(1)


Now Bob has F_T number of 10 dollar bills (plus T_T fives - because they have same number of bills) and he has total $90. Thus:

10*F_T + 5*T_T = 90..................................................(2)

Now you have two equations and two unknowns - solve it....