Posted in: Basic Maths Skills

# Repeating decimal to fraction and number facts

Revision for the Grade 8 maths exam does not have to be stressful. Making flashcards, memorising maths key facts, or memorising the repeating decimal to fraction number can help you as you prepare for the coming maths exams.

Below are key facts and maths skill that you can master in 10 minutes. The multiplication and division tricks and tips below will make a world of difference when you take the Grade 8 maths exam.

## 1 is not a prime number

For a number to be a prime number it must have only two factors, 1 and itself. 1 has only 1 factor, 1.

First 10 prime numbers: 2,3,5,7,11, 13,17, 19, 23,…

• 9 is odd number, not prime number with factors {1,3,9}
• 15 is odd number, not prime number with factors {1,3,5,15}

## List of common and repeating decimal to fraction and percentages

½=50%=0.5
⅓=33⅓%=33.3…
¼=25%=0.25
⅕=20%=0.2
⅛=12.5%=0.125
¹/10=10%=0.1
⅔=66⅔%=66.6…
⅖=40%=0.4
¾=75%=0.75
⅗=60%=0.6

Take the online Fraction Quiz to test your knowledge.

## ×12 Recall Tip

12×1=1 2
12×2=2 4
12×3=3 6
12×4=4 8
12×5=6 0
12×6=7 2
12×7=8 4
12×8=9 6
12×9=10 8
12×10=12 0
12×11=13 2
12×12=14 4

• Starting numbers increase in 1,2,3…*
• Multiples of ×12 end in 0,2,4,6 or 8 and reoccur after 5 numbers
• Only applies to ×12

123 + 573
=(100 + 20 + 3) + (500 + 70 + 3)
= 100 + 500 + 20 + 70+ 3 + 3
= 600 + 90 + 6
= 696

## Mental tips for division by a decimal

270 ÷ 0.3
🚦make 0.3 whole number by × 10
I.e. 270 × 10 = 2700; 0.3 ×10= 3

Now, 2700 ÷ 3 = 900

Top tip: In division by decimals, multiply the dividing numbers by 10, 100,… to change decimal numbers to whole numbers

#NumberSkills #CoolTips

## Dividing with decimal numbers

E.g. 80÷1.5
🚦×10 make 1.5 whole
80×10=800; 1.5×10=15
–‐‐—————-‐–
🚦simplify
800÷15… ÷5
=160÷3
🚦partition 160…150+10
(150÷3)+(10÷3)
=50+3⅓
=53⅓ (or 53.33…)

*Tip: make the decimal a whole number; then simplify, partition and solve.

## Dividing 3-digit numbers

836 ÷ 32
🚦split 836 into easily divisible numbers
|640 | 160 | 32 | 4 …sum is 836
÷| 32 | 32 | 32 | 32 …divisor is 32
——–‐‐——————-
20 + 5 + 1 + ⅛ = 26⅛ or 26.125

Tip: Go by 20, 10, 5 to reduce 3 digit numbers like 836. You can also apply the same technique to simplify even bigger numbers.

#NumberFacts

## Mental multiplication of big numbers

53 × 37
○ 50 | 30
● 3 | 7
-‐——————-‐–
○50×30=1,500
○50×7= 350
●3×30= 90
●3×7= 21
————————-
1,500 + 350 + 90 + 21 = 1,961

#MentalMathTips

53 × 37
———–
53
×37
””””””’
371
+ 159
””””””””””

## Divide with Common and Repeating Decimal to Fraction

E.g.280 ÷ 3½
🚦Convert fraction to decimal 3½=3.5
280÷3.5
🚦multiply 280 and 2.5 by 10 to make 3.5 whole numbers before dividing.

= 2,800÷35
💡35 × 8 = 280
If 35×8=280🔁280÷35=8, so 2800÷35=80
———————-
So, 280÷3½
=280÷3.5
=2,800÷35
=80

#MentalDivision

## Basic maths skills: Tips and Study Guides

We have a collection of Grade 8 topics and study guides that you might find useful when planning for the year or just brainstorming the maths course. Check it out.