r × t = w
↓
5 × t = 100
Solve for t: t = 20 seconds.- B Let s = Sam’s rate. Bob’s rate is thus 2s, and their combined rate is s + 2s = 3s.
Now use the r × t = w formula to find the value for s.
r × t = w
↓
3 s × 12 = 1
36 s = 1
s = 361
Bob’s rate is twice Sam’s rate, so Bob’s rate is 2( 361 ) = 181. Now plug this rate into
the r × t = w formula.
r × t = w
↓
181 × t = 1
t = 18 - D Use the r × t = w table to determine the number of minutes it will take
Machine A to produce 40 more widgets than machine B. Machine A’s rate is
widgets/minute =^152 , and Machine B’s rate is widgets/minute =^203. Since the
machines start at the same time, use t to represent each of their times. Plug
these values into the table.
r × t = w
↓
Machine A 152 t =^152 t
Machine B 203 t =^203 t
Represented algebraically, Machine A’s work is thus^152 t and Machine B’s
work is^203 t. You know that Machine A produces 40 more widgets, so
15 t
2 = 40 +
20 t
3. Now solve for t:
Bring t to one side: 152 t –^203 t = 40
↓
Get a common denominator: 456 t –^406 t = 40
↓352 PART 4 ■ MATH REVIEW04-GRE-Test-2018_313-462.indd 352 12/05/17 12:04 pm