JAMB Mathematics · Section I
Study notes for Fractions, Decimals, Approximations — part of the JAMB UTME Mathematics syllabus. 3 learning objectives with explanations and exam tips.
When you're working with fractions and decimals, the key is understanding they're just different ways of showing the same thing. A fraction like ¾ is exactly the same as 0.75 in decimal form. To convert, you simply divide the numerator by the denominator.
Approximations help when exact answers get messy. If a calculation gives you 2.7348, you might round it to 2.73 or even 2.7 depending on what's asked. Think of it like sharing ₦5,000 among 3 people—you can't give exact equal amounts, so you approximate.
When adding or subtracting fractions, find a common denominator first. For decimals, line up the decimal points carefully. Multiplying fractions is straightforward: multiply across the top and bottom. Division means flip the second fraction and multiply.
Working with fractions and decimals involves the same operations you use daily: addition, subtraction, multiplication, and division. When adding or subtracting fractions, you need a common denominator first. For instance, if you're sharing ₦1000 between two people where one gets 3/5 and another gets 1/4, you'd convert to twentieths: 12/20 plus 5/20 equals 17/20 of the money.
Multiplication of fractions is simpler—just multiply numerators together and denominators together. Division requires flipping the second fraction before multiplying. With decimals, these operations follow similar patterns to whole numbers, though you must carefully place the decimal point in your final answer. Approximations help when exact answers aren't needed; rounding to decimal places or significant figures saves time during calculations.
Significant figures are the important digits in a number that carry real meaning. When you express a number to a certain number of significant figures, you're keeping only the most important digits and rounding the rest away. Think of it like this: if a trader in Lekos Market weighs rice and gets 2,547.3 grams, expressing it to 3 significant figures gives 2,550 grams—you've kept the three most meaningful digits and rounded.
The rule is straightforward. Start counting from the first non-zero digit on the left. All digits after that count as significant, including zeros between them or at the end if there's a decimal point. For example, 0.00456 expressed to 2 significant figures becomes 0.0046.