Solve a formula for one letter

Answer Key - Grade 9 Math Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Pia (and a very loud bell) knows d = rt: distance d, speed r, time t. Split both sides by r. Solve d = rt for t.

   t = d/r
2. 2.

   A robot's circuit follows V = IR: volts V, current I, resistance R. Split both sides by I. Tala solves for R.

   R = V/I
3. 3.

   Zee buys n pencils at p cents each, so C = np. Split both sides by n. Solve C = np for p.

   p = C/n
4. 4.

   Ari's fence has perimeter P = 2l + 2w. The first step gives P − 2w = 2l. Solve for l.

   l = (P − 2w)/2
5. 5.

   Bo's line is y = mx + b. The first step gives y − b = mx. Solve for x.

   x = (y − b)/m
6. 6.

   Esme's speed is v = u + at. The first step gives v − u = at. Solve for t.

   t = (v − u)/a
7. 7.

   Kira's fence has perimeter P = 2l + 2w. Which formula is solved for w?

   • w = (P − 2l)/2
   • w = (P + 2l)/2
   • w = P − l
   • w = 2(P − 2l)
8. 8.

   Luz's line is y = mx + b. Which formula is solved for m?

   • m = (y − b)/x
   • m = (y + b)/x
   • m = x(y − b)
   • m = y − b/x
9. 9.

   Milo's speed is v = u + at. Which formula is solved for a?

   • a = t(v − u)
   • a = (v − u)/t
   • a = (v + u)/t
   • a = v − u/t
10. 10.

    Noah's game gives N = 5c − 12 points for c coins. Which formula is solved for c?

    • c = (N + 12)/5
    • c = (N − 12)/5
    • c = 5(N + 12)
    • c = N + 12/5