SAT Math · Linear functions · easy

A linear function p satisfies p(0) = 6 and p(4) = 22. What is the value of p(10)?

A linear function pp satisfies p(0)=6p(0) = 6 and p(4)=22p(4) = 22. What is the value of p(10)p(10)?

Answer and explanation

Answer: 46

The value p(0)=6p(0) = 6 is the yy-intercept. The slope is 22−64−0=4\frac{22 - 6}{4 - 0} = 4, so p(x)=4x+6p(x) = 4x + 6. Then p(10)=4(10)+6=46p(10) = 4(10) + 6 = 46. Check against the other point: p(4)=16+6=22p(4) = 16 + 6 = 22. Equivalently, p(10)=p(4)+4(6)=22+24=46p(10) = p(4) + 4(6) = 22 + 24 = 46. A common wrong answer is 26, which comes from adding the slope once, 22+422 + 4. Another is 40, from forgetting the intercept (computing 4×104 \times 10), and a third is 16, the change in output between the two known points. Multiply the slope by the full change in xx.

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