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.

   Ren's rug has area A = lw: length l, width w. Split both sides by l. Solve A = lw for w.

   w = A/l
3. 3.

   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
4. 4.

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

   p = C/n
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.

   Jun's triangle has two equal sides a and a base b, so P = 2a + b. The first step gives P − b = 2a. Solve for a.

   a = (P − b)/2
8. 8.

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

   • w = 2(P − 2l)
   • w = (P + 2l)/2
   • w = (P − 2l)/2
   • w = P − l
9. 9.

   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
10. 10.

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

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