GCSE Maths

XYZ-myexam

Edexcel · Algebra

Introduction

Operations are the basic processes used to manipulate numbers and expressions. The four fundamental operations are:

  • Addition (+)
  • Subtraction (-)
  • Multiplication (x)
  • Division (÷)

Operations with Fractions

In mathematics, an Operation is a process or action that produces a new value from one or more inputs, such as addition, subtraction, multiplication, or division.

Order of Operations:

To solve expressions correctly, follow the order:

1
Parentheses
2
Exponents
3
Multiplication / Division
4
Addition / Subtraction

Addition of Fractions

1. Same Denominator

If the denominators (bottom numbers) are the same, just add the numerators (top numbers):

Example
Evaluate: $\frac{3}{4}+\frac{2}{4}$
SOLUTION
$$\frac{3}{4}+\frac{2}{4}=\frac{6}{4}$$

2. Different Denominators

If the denominators are different, follow these steps:

1
Find the Least Common Denominator (LCD). The smallest number that both denominators can divide into.
2
Convert fractions to have the same denominator
3
Add the numerators
4
Simplify the result (if needed)
Example
Evaluate: $\frac{3}{4}+\frac{7}{8}$
SOLUTION
$$\frac{3}{4}+\frac{7}{8}=\frac{3(8)+7(4)}{32}=\frac{52}{32}$$

Final Answer: $\frac{13}{8}$

Solved Example
Convert $3/4+7/2$ as a fraction
SOLUTION
1
Make the bottom numbers the same
$$=\frac{3}{4}+\frac{7}{2}$$
$$=\frac{3+14}{4}$$
2
Add the top numbers
$$=\frac{17}{4}$$
3
Convert back to a Mixed Fraction
$$=3\frac{5}{4}$$

Final Answer: $3\frac{5}{4}$

Subtraction of Fractions

1. Same Denominator

If the denominators (bottom numbers) are the same, subtract the numerators (top numbers):

Example
Evaluate: $\frac{9}{4}-\frac{2}{4}$
SOLUTION
$$\frac{9}{4}-\frac{2}{4}=\frac{7}{4}$$

2. Different Denominators

If the denominators are different, follow these steps:

1
Find the Least Common Denominator (LCD). The smallest number that both denominators divide into.
2
Convert fractions to have the same denominator
3
Subtract the numerators
4
Simplify the result (if possible)
Example
Evaluate: $\frac{3}{8}-\frac{1}{3}$
SOLUTION
$$\frac{3}{8}-\frac{1}{3}=\frac{3(3)-8(1)}{24}$$

Final Answer: $\frac{1}{24}$

Solved Example
Convert $\frac{9}{4} – \frac{5}{3}$ as a fraction
SOLUTION
1
Make the bottom numbers the same
$$=\frac{9}{4}-\frac{5}{3}=\frac{9(3)-5(4)}{12}$$
2
Subtract the top numbers
$$=\frac{7}{12}$$

Final Answer: $\frac{7}{12}$

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Multiplication of Fractions

Multiplying fractions is straightforward-just multiply numerators together and denominators together, then simplify if possible.

1. Basic Rule: For a problem, such as

$$\frac{a}{b}\times\frac{c}{d}=\frac{a\times c}{b\times d}$$
  • Numerator of the product $=a\times c$
  • Denominator of the product $=b\times d$

2. Steps with Simplification

1
Multiply the numerators: $a\times c$.
2
Multiply the denominators: $b\times d$.
3
Simplify the resulting fraction by dividing numerator and denominator by their greatest common divisor (GCD).
Example
Multiply: $\frac{2}{3}\times\frac{6}{5}$
SOLUTION
$$\frac{2}{3}\times\frac{6}{5}=\frac{2\times6}{3\times5}$$
$$=\frac{12}{15}$$

Final Answer: $\frac{4}{5}$

Solved Example
Convert $8/3\times6/5$ as a fraction
SOLUTION
1
Multiply top numbers together.
$$=\frac{8}{3}\times\frac{6}{5}$$
2
Multiply bottom numbers together.
$$=\frac{8\times6}{3\times5}$$
3
Simplify the result
$$=\frac{48}{15}$$

Final Answer: $\frac{48}{15}$

Division of Fractions

Dividing fractions involves multiplying by the reciprocal (or “flip”) of the divisor.

1. Basic Rule: For a problem, such as

$$\frac{a}{b}\div\frac{c}{d}=\frac{a\times d}{b\times c}$$
  • Numerator of the product $=a\times d$
  • Denominator of the product $=b\times c$

2. Steps with Simplification

1
Write the problem:
$$\frac{a}{b}\div\frac{c}{d}$$
2
Reciprocal, Change to
$$\frac{a}{b}\div\frac{c}{d}=\frac{a\times d}{b\times c}$$
3
Multiply numerators and denominators. Simplify the result by dividing numerator and denominator by their greatest common divisor (GCD).
Example
Divide: $\frac{3}{4}\div\frac{2}{7}$
SOLUTION
$$\frac{3}{4}\times\frac{7}{2}=\frac{21}{8}$$

Final Answer: $\frac{21}{8}$

Solved Example
Convert $3/4\div7/2$ as a fraction
SOLUTION
1
Keep the first fraction same and change the divide sign to multiplication sign and reciprocate the second fraction.
$$=\frac{3}{4}\times\frac{2}{7}$$
2
Multiply bottom and top numbers together.
$$=\frac{6}{28}$$

Final Answer: $\frac{6}{28}$

Solved Examples

Solved Example
Emma baked $2/3$ of a tray of cookies in the morning and $1/4$ of a tray in the afternoon. How much of a full tray did she bake in total?
SOLUTION
1
Write down the given information
  • In Morning, Emma baked:- $\frac{2}{3}$
  • At afternoon, fraction of tray gets completed: $\frac{1}{4}$
2
Simplify to make a common denominator. We know that:
$$\frac{2\times4}{3\times4}=\frac{8}{12}$$
$$\frac{1\times3}{4\times3}=\frac{3}{12}$$
3
Calculate the final result by applying favorable operations. The total amount of baking that has been completed: $=(\frac{8}{12}+\frac{3}{12})$
$$=\frac{8+3}{12}=\frac{11}{12}$$

Final Answer: $\frac{11}{12}$

Solved Example
A ribbon is $2\frac{3}{4}$ meter long. You need pieces of length $\frac{1}{6}$ meter. How many full pieces can you cut?
SOLUTION
1
Write down the given information
  • Length of ribbon:- $2\frac{3}{4}=\frac{11}{4}$
  • Pieces of length :- $\frac{1}{6}$
2
Divide total length by piece length. We know that:
$$=\frac{\frac{11}{4}}{\frac{1}{6}}$$
$$=\frac{11\times6}{4\times1}$$
3
Calculate the final result by applying favorable operations. Pieces that we can cut from $11/4$m length of ribbon: $\frac{11\times6}{4\times1}=\frac{66}{4}$
$$=\frac{66}{4}=\frac{33}{2}=16.5$$

Final Answer: Therefore, we can cut 16 full pieces from that ribbon.

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