Question

Krista was assigned a homework problem that stated there were 45 stamps purchased for $18.75. Some stamps were 40 cents, and some stamps were 55 cents. To solve this problem, she wrote the system of equations that is shown below. 0.40 x + y = 45. x + 0.55 y = 18.75. Which explains the error that Krista made? Krista put 0.40 in the first equation meant for the number of stamps. Krista put 0.55 in the second equation meant for the value of stamps. Krista did not use the correct decimal to represent the total cost of the stamps. Krista mistakenly put 45 in the first equation when it should have been in the second equation.
PLEASE HURRY I REALLY NEED HELP WILL GIVE BRAINLIEST

Answer 1

Answer:

a

Step-by-step explanation:

Answer 2

Answer: Krista put 0.40 in the first equation meant for the number of stamps

Step-by-step explanation: From the information available to Krista, she can determine the number of stamps that cost 40 cents and those that cost 55 cents. What she needs is a system of simultaneous equations both of which would use the total number of stamps and the total cost of stamps to determine the how many stamps cost 40 cents and how many costs 55 cents.

The system of equations should have been,

x + y = 45 ----------(1)

0.40x + 0.55y = 18.75 ----------(2)

From equation (1), let x be the subject of the equation and hence x = 45 - y

Substitute for the value of x into equation (2)

0.40(45 - y) + 0.55y = 18.75

18 - 0.40y + 0.55y = 18.75

Collect like terms and you now have

0.55y - 0.40y = 18.75 - 18

0.15y = 0.75

Divide both sides of the equation by 0.15

y = 5

When y has been calculated as 5, substitute for the value of y into equation (1)

x + y = 45

x + 5 = 45

x = 45 - 5

x = 40

The results show that the stamps that cost 0.40 cents (x) were 40 in number while those that cost 0.55 cents (y) were 5 in number.

This answer could not have been derived due to the mistake Krista committed when writing the equations.