Last reviewed: 25 October 2026
Decimals and percentages turn up everywhere in upper primary Mathematics: in money, measurement, data and word problems. A learner who is confident with place value and conversion picks up easy marks across a whole paper. This guide covers each skill with short examples you can copy into an exercise book. Decimals are a sub-strand of Numbers in KICD’s Grade 6 Mathematics curriculum design.
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Place Value in Decimals
The decimal point separates whole numbers from parts of a whole. In 34.275, the 2 is tenths, the 7 is hundredths and the 5 is thousandths. So 34.275 means 34 + 2/10 + 7/100 + 5/1000. Learners often think 0.45 is smaller than 0.4 because “4 is less than 45”, or that 0.45 is bigger than 0.5. Writing both with the same number of decimal places fixes this: 0.45 and 0.50, so 0.5 is larger.
Rounding Decimals
Look at the digit just after the place you are rounding to. If it is 5 or more, round up; if it is 4 or less, keep the digit. 7.368 to one decimal place is 7.4; to two decimal places it is 7.37. Money is usually rounded to two decimal places, the nearest ten cents being shown as 0.10.
Adding and Subtracting Decimals
Line up the decimal points, fill empty places with zeros, then work as with whole numbers.
- 12.5 + 3.47 = 12.50 + 3.47 = 15.97
- 20 − 6.35 = 20.00 − 6.35 = 13.65
Multiplying Decimals
Multiply as if there were no decimal points, then count the total number of decimal places in the question and put that many in the answer. 2.4 × 0.3: 24 × 3 = 72, and there are two decimal places in the question, so the answer is 0.72. Multiplying by 10, 100 or 1000 moves the digits one, two or three places to the left: 3.56 × 100 = 356.
Dividing Decimals
When dividing by a whole number, keep the decimal point in line: 7.5 ÷ 3 = 2.5. When dividing by a decimal, multiply both numbers by 10 or 100 until the divisor is whole. 4.8 ÷ 0.6 becomes 48 ÷ 6 = 8. Dividing by 10, 100 or 1000 moves digits to the right: 45 ÷ 100 = 0.45.
Percentages Explained
“Per cent” means “out of 100”. So 35% = 35/100 = 0.35. Three conversions cover almost every question:
- Percentage to fraction: write over 100 and simplify. 40% = 40/100 = 2/5.
- Fraction to percentage: multiply by 100. 3/4 × 100 = 75%.
- Decimal to percentage: multiply by 100. 0.08 = 8%.
Learning a few by heart saves time: 1/2 = 50%, 1/4 = 25%, 3/4 = 75%, 1/5 = 20%, 1/10 = 10%.
Finding a Percentage of an Amount
To find 15% of KSh 2,400, change 15% to 15/100 and multiply: 15/100 × 2,400 = KSh 360. A mental shortcut: 10% of 2,400 is 240, and 5% is half of that, 120, so 15% is 360. To write one amount as a percentage of another, make a fraction and multiply by 100: 18 out of 24 is 18/24 × 100 = 75%.
Money and Shopping Problems
Exam questions often use prices, discounts and change.
- A pair of shoes costs KSh 1,800 and has a 10% discount. Discount = KSh 180, so the price paid is KSh 1,620.
- Otieno buys 3 pens at KSh 25.50 each and pays with a KSh 100 note. Cost = KSh 76.50, so his change is KSh 23.50.
- A class of 40 has 24 girls. The percentage of girls is 24/40 × 100 = 60%.
Checking Answers
Estimate first. If 2.4 × 0.3 should be “a bit less than 1”, an answer of 7.2 is clearly wrong. A percentage of an amount less than 100% must be smaller than the amount. These quick checks catch most slips in a multiple-choice paper.
Keep Practising
Use the free daily questions on the exam countdown, then let the What to Revise report point to weak topics. Our Grade 6 fractions guide pairs well with this one, and the Grade 6 Mathematics papers give exam-style practice. The full papers with worked answers are in the Monthly Pass at KSh 500 by M-Pesa, and our questions are checked by a teacher.
Ten-minute check: try the free Grade 6 CBC Challenge. It has 10 questions, each marked on the spot with the working, and it shows which topics to practise next.