Solving using 2 equations in two variable: Jason bought a total of 7 postcards for 1.80. If small cost 20 cents and the large ones cost 30 cents, how many postcards of each size did he buy?
answered here:
https://www.jiskha.com/display.cgi?id=1198461333
I am confused.
geesh, all they did was change the numbers.
here is a start:
small stamps ---- s
large stamps ---- l
s+l = 7 **
20s + 30l = 180 ---> 2s + 3l = 18 ***
solve the two equations ** and ***
or
small ones ---- s
larger ones ---- 7-s
20s+30(7-s) = 180
solve for s, then 7-s
thank you
To solve this problem using two equations in two variables, let's introduce two variables:
Let's say Jason bought x small postcards and y large postcards.
Now we can set up two equations based on the information given:
1) The total number of postcards: x + y = 7 (Equation 1)
(The sum of the number of small postcards, x, and the number of large postcards, y, is equal to 7.)
2) The total cost of the postcards: 0.20x + 0.30y = 1.80 (Equation 2)
(The cost of each small postcard, 0.20, multiplied by the number of small postcards, x, plus the cost of each large postcard, 0.30, multiplied by the number of large postcards, y, is equal to 1.80.)
Now that we have two equations, we can solve them simultaneously to find the values of x and y.
There are different methods to solve these equations, such as substitution, elimination, or graphing. Here, we will solve them using the method of substitution:
1) Solve Equation 1 for x in terms of y:
x = 7 - y
2) Substitute x in Equation 2 with the value from Step 1:
0.20(7 - y) + 0.30y = 1.80
Simplify the equation:
1.40 - 0.20y + 0.30y = 1.80
Combine like terms:
0.10y = 0.40
Divide both sides by 0.10:
y = 0.40 / 0.10
y = 4
Now, substitute the value of y back into Equation 1 to find x:
x + 4 = 7
Subtract 4 from both sides:
x = 7 - 4
x = 3
So, Jason bought 3 small postcards and 4 large postcards.