Question

You want to prepare a test that contains 20 questions worth 50 points overall. How many 2-point and 4-point questions can you include in the test?

A. 5, 10
B. 10,10
C.  12, 8
D. 15, 5

Answer 1

you can do it this way. (2y+4x=50) y is the number of 2 point questions and x is the number of 4 point questions. and (x+y=20) so now choose one of the equations to solve for x or y and then input that value into the other equation. like this x=20-y is the same as x+y=20 so in place of x in the other equation you put 20-y... 2y+4(20-y)=50 then you solve for y in this equation 2y+80-4y=50 then simplify to -2y+80=50 then get y by itself -2y=50-80 or -2y=-30 then divide both sides by -2 so y equals 15. then put the y value back into the x+y=20 equation and you will get 5 for x.

so your answer is D.

Answer 2

D. because 15+5= 20 questions and 15 * 2 =30 and 5*4 =20 which add to 50. they trick you with letter A but 10 + 5 is only 15 questions, hope i helped.