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Door 7 Β· Grade 4

πŸ”’ Equivalent Fractions

A fraction ab has a numerator (top) and a denominator (bottom)

β–Ά Play Door 7

Generate Equivalent Fractions

What is a Fraction?
A fraction names a part of a whole. It is written as numeratordenominator. The denominator (bottom number) tells how many equal parts the whole is divided into; the numerator (top number) tells how many of those parts we take. So 34 means 3 out of 4 equal parts.
What are Equivalent Fractions?
Equivalent fractions are fractions that look different but name the same amount. For example 12, 24 and 48 all cover exactly half of a bar they are equivalent.
How to Make an Equivalent Fraction
Multiply or divide the numerator and the denominator by the same non-zero number. Whatever you do to the top, you must do to the bottom:
12=1Γ—2/2Γ—2=24=1Γ—3/2Γ—3=36
Simplest Form
A fraction is in simplest form when the top and bottom share no common factor except 1. To simplify, divide both by their highest common factor. For example 68=6Γ·28Γ·2=34.
Fraction×…

Worked example

Problem: Write two fractions equivalent to 12.

  1. Multiply top and bottom by 2: 1Γ—22Γ—2=24
  2. Multiply top and bottom by 3: 1Γ—32Γ—3=36
  3. Answer: 24 and 36

Answer: Answer: 24 and 36

Compare Fractions with Unlike Denominators

Comparing fractions means deciding which one is larger (or whether they are equal). There are three simple cases.
Case 1 Same denominator. If the bottoms are equal, the fraction with the bigger numerator is bigger: 35>25.
Case 2 Same numerator. If the tops are equal, the fraction with the smaller denominator is bigger fewer pieces means each piece is larger: 14>18.
Case 3 Unlike denominators. Make the denominators the same first, then compare the tops:
β€’ Find a common denominator (usually the LCM of the two denominators).
β€’ Rewrite each fraction as an equivalent fraction with that denominator.
β€’ Compare the numerators.

Example: compare 23 and 34. The LCM of 3 and 4 is 12:
23=8/12 34=9/12β‡’ 34>23
Benchmark trick. Compare each fraction to 12. Since 38 is less than 12 and 58 is more than 12, we know 58>38 without any calculation.
Symbols: > means greater than, Common…

Worked example

Problem: Which is greater, 35 or 25?

  1. Same denominator, so compare the tops.
  2. 3>2
  3. Answer: 35

Answer: Answer: 35

Add and Subtract Fractions with Same Denominator

When two fractions have the same denominator, adding or subtracting them is easy: keep the denominator and just add (or subtract) the numerators.
a/d+b/d=a+b/d a/d-b/d=a-b/d
Why the bottom stays the same: the denominator tells the size of each piece. When we put pieces together or take some away, the size of a piece does not change only how many we have changes. So only the numerators are added or subtracted.
Examples: 15+25=35 and 45-15=35.
Always simplify the answer when you can:
26=2Γ·2/6Γ·2=13
Improper fractions. If the top becomes bigger than the bottom, the answer is more than one whole. For example 35+45=75, which is the same as 125.
Common mistake to avoid: do not add the denominators. 15+25 is 35, never 310.

Worked example

Problem: Find 15+25.

  1. Same denominator, so add the tops: 1+2=3.
  2. Keep the bottom: 5.
  3. Answer: 35

Answer: Answer: 35