Answer:
Step-by-step explanation:
You pretty much have to do A, to get at B.
This is what is called a Diophantine equation. The answer much be a whole number. So we'll set one of the conditions up. There's not much room to move around to get the first answer.
Equations
Let x be the number of 2 point questions.
Let y be the number of 1/2 deductions.
Let z be the number of questions that are not answered.
Solutions
z = 0 (All questions are answered)
x + y = 50
2x - 1/2 y = 80 Multiply this equation by 2
4x - y = 160 Add the first equation to this one.
x + y = 50
5x = 210 Divide by 5
5x/5 = 210/5 Do the division
x = 42
x + y = 50 Substitute x = 42 into this equation
42 + y = 50 Subtract 42 from both sides
42-42 + y = 50-42 Do the subtraction
y = 8
One solution is x=42 and y = 8
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I can find no other solutions that will work. If he can get over 80 then if he answers 44 correctly and leaves the rest blank, his mark is 88
If he answers 43 correctly and leaves the rest blank is mark is 86
If he answers 45 and leaves 5 blank, his mark is ninety. In each case, he doesn't get any wrong.
