Time & Work
0/10 problems solved
Formulas & 30-Second Shortcut Tricks
Formulas
- If A finishes work in a days, A's 1-day work = 1/a
- Together: 1/a + 1/b = 1/T ⇒ T = ab/(a+b)
- Work = Rate × Time (men × days × hours is constant for the same job)
- M1·D1·H1 / W1 = M2·D2·H2 / W2
Shortcuts
- LCM method: take total work = LCM(a, b) units; each person's rate = LCM / days.
- Two people together: product ÷ sum (ab/(a+b)) — no fractions needed.
- If A is k times as efficient as B, A takes 1/k of B's time.
Practice problems
A can finish a job in 20 days and B in 30 days. Working together, how many days will they take?
12 workers can build a wall in 18 days. How many days will 6 workers take to build the same wall?
A can finish a job in 10 days and B in 40 days. Working together, how many days will they take?
24 workers can build a wall in 12 days. How many days will 8 workers take to build the same wall?
A can finish a job in 18 days and B in 36 days. Working together, how many days will they take?
12 workers can build a wall in 30 days. How many days will 6 workers take to build the same wall?
A can finish a job in 10 days and B in 40 days. Working together, how many days will they take?
12 workers can build a wall in 20 days. How many days will 10 workers take to build the same wall?
A can finish a job in 12 days and B in 24 days. Working together, how many days will they take?
15 workers can build a wall in 20 days. How many days will 6 workers take to build the same wall?
Time & Work Speed Test
1 minute per question. Use the palette to jump around; you'll see time spent on every question at the end.