Certificates / Quantitative aptitude / Time and Work
Time and Work: lesson, then the certificate test
Step 1: the lesson (about 1 min)
Think in work per day: someone who finishes a job in n days does 1/n of it each day.
- Working together, ADD the per-day work, never the days.
- Easy trick: take the total work as the LCM of the days, then work out each person's units per day.
- Days needed = total work ÷ work per day.
Worked example
A can finish a job in 12 days and B in 15 days. How long do they take together?
- Total work = LCM(12, 15) = 60 units
- A does 5 units a day, B does 4 units a day: 9 units a day together
- 60 ÷ 9 = 6⅔ days
Answer: 6⅔ days
Watch out
- Adding the days (12 + 15) or averaging them is always wrong.
Made by Shishya (AI-assisted): a general method in our own words, with our own example; no exam or platform question is copied.
Step 2: the test
- 15 questions from Shishya's checked question bank, 20 minutes. Pass mark: 11 correct.
- Scored on Shishya's server; the answers are not shown afterwards, so the test stays fair. Each attempt draws new questions.
- Free. Your first test needs no account; sign up free to take more. Your answers and score are not stored; if you pass, you choose the name to print (ages 13 and up).
- It is a Shishya completion certificate — not a university or government credential. The test is not supervised.