Term
24/7 hours or 3 3/7 hours
(Take Product over Sum: 8*6/(8+6) and simplify) |
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Definition
| Working alone, Jim works a job in 8 hours. Working alone, Jane works a job in 6 hours. If they work together, then how long does it take to do the job? |
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Term
| 5 hours (Take Product over Difference: 4*20/(20-4) and simplify) |
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Definition
| Working together, Jim and Jane work a job in 4 hours. Working alone, Jane takes 20 hours to do the job. How long does it take Jim to work the job working alone? |
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Term
| 12 ohms (Take Product over Sum: 20*30/(20+30) and simplify) |
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Definition
| A parallel circuit has two branches with resistances of 20 and 30 ohms, respectively, in the branches. What is the effective resistance of the parallel circuit? |
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Term
| 90 ohms (Take Product over Difference: 36*60/(60-36) and simplify) |
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Definition
| A parallel circuit has an effective resistance of 36 ohms. One branch has a resistance of 60 ohms. What is the resistance in the other branch? |
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Term
| 25/13 feet or 1 12/13 feet (Take Product over Sum: 50*2/(50+2) and simplify) |
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Definition
| What should the focal length of a lens be if an object 50 feet away from the lens is to be projected on a surface 2 feet away from the lens? |
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Term
| 10 feet (Take Product over Difference: 40*8/(40-8) and simplify) |
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Definition
| A lens has a focal length of 8 feet. An object is 40 feet away from the lens. How far from the lens should the film be from the lens so that the object is in focus? |
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Term
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Definition
| What is the formula that relates the focal length f of a lens to the distance do from the object to the lens to the distance di from the image of the object to the lens? |
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Term
| f = (do*di)/(do + di), which is a product over sum |
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Definition
| What formula is obtained when one solves 1/f = 1/do + 1/di for f? |
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Term
| do = (f*di)/(di - f), or di = (f*do)/(do - f), both of which are a product over difference |
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Definition
| What formula is obtained when one solves 1/f = 1/do + 1/di for do (or di)? |
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Term
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Definition
| What is the formula that relates the time t1 it takes a person to do a job by themselves, the time t2 it takes another person to do a job by themselves, and the time t it takes to do the job when the two people work together? |
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Term
| t = (t1*t2)/(t1 + t2), which is a product over sum |
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Definition
| What formula is obtained when one solves the equation 1/t = 1/t1 + 1/t2 for t? |
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Term
| t1 = (t*t2)/(t2 - t), or t2 = (t*t1)/(t1 - t), both of which are a product over difference |
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Definition
| What formula is obtained when one solves 1/t = 1/t1 + 1/t2 for t1 (or t2)? |
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Term
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Definition
| What is the formula that relates the effective resistance r of a parallel circuit with 2 branches, the resistance r1 in the first branch, and the resistance r2 in the second branch? |
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Term
| r = (r1*r2)/(r1 + r2), which is a product over sum |
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Definition
| What formula is obtained when one solves the equation 1/r = 1/r1 + 1/r2 for r? |
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Term
| r1 = (r*r2)/(r2 - r), or r2 = (r*r1)/(r1 - r), both of which are a product over difference |
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Definition
| What formula is obtained when one solves 1/r = 1/r1 + 1/r2 for r1 (or r2)? |
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