US High School Solving a Formula for a Variable — practice questions

Explore 2 free Solving a Formula for a Variable questions in US High School Mathematics. Open each question or exercise to read its content, reference answers and available explanation.

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Solving a Formula for a Variable questions and exercises with answers

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Solve 8x + 7y = 15 for y.Read the answer and worked solution →Solve A = P + Prt for t.Read the answer and worked solution →

Worked practice questions

Solve 8x + 7y = 15 for y.

y is 15 plus 8x, over 7
y is 15 minus 8x, over 7
y is 8x minus 15, over 7
y is 15 minus 8x, over 8

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Correct answer: B. y is 15 minus 8x, over 7

1. Treat y as the variable to isolate and everything else as a known quantity. 2. Subtract 8x from both sides to get 7y equal to 15 minus 8x. 3. Divide both sides by 7 to get y equal to 15 minus 8x, all over 7. 4. Adding 8x instead of subtracting it flips the sign and gives a different line. _Source: OpenStax Intermediate Algebra (CC BY 4.0), Ch 2 "Solving Linear Equations", section 2.3 Solve a Formula for a Specific Variable_

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Solve A = P + Prt for t.

t is A plus P, over Pr
t is P minus A, over Pr
t is A minus P, over Pt
t is A minus P, over Pr

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Correct answer: D. t is A minus P, over Pr

1. The term holding t is Prt, so isolate that term first. 2. Subtract P from both sides to get A minus P equal to Prt. 3. Divide both sides by Pr to get t equal to A minus P, all over Pr. 4. Dividing by Pt would leave t on both sides, so nothing would be solved. _Source: OpenStax Intermediate Algebra (CC BY 4.0), Ch 2 "Solving Linear Equations", section 2.3 Solve a Formula for a Specific Variable_