Certificates / Quantitative aptitude / Percentage
Percentage: lesson, then the certificate test
Step 1: the lesson (about 1 min)
Per cent means "out of 100": x% of N = N × x ÷ 100.
- Know the common fractions: 10% = 1/10, 20% = 1/5, 25% = 1/4, 12.5% = 1/8, 50% = 1/2.
- Percentage change = change ÷ ORIGINAL value × 100.
- Two changes one after the other, a% then b%: net change = a + b + (a × b ÷ 100). Use a minus sign for a fall.
Worked example
A price rises by 20% and then falls by 10%. What is the net change?
- a = 20, b = −10
- 20 + (−10) + (20 × −10 ÷ 100) = 10 − 2 = 8
Answer: An 8% rise.
Watch out
- A 20% rise followed by a 20% fall is not zero: 20 − 20 − 4 = a 4% fall.
- Always divide by the original value, not the new one.
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.