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Middle SchoolNumber System
Decimals & Percentages
Working with decimal numbers and percentages
Master decimals and percentages — essential for real life calculations.
✓ Decimal point separates whole from fract...✓ % means per hundred: 75% = 75/100 = 0.75✓ To find X% of Y: (X/100) × Y
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📖 Understanding Decimals & Percentages
A decimal number has a whole number part and a fractional part separated by a decimal point. For example 3.75 = 3 + 7/10 + 5/100.
The digits after the decimal point represent tenths, hundredths, thousandths etc. So 0.1 = 1/10, 0.01 = 1/100, 0.001 = 1/1000.
A percentage is a fraction with denominator 100. The symbol % means 'per hundred'. So 45% = 45/100 = 0.45.
To convert percentage to decimal: divide by 100. To convert decimal to percentage: multiply by 100. To find a percentage of a number: multiply by the percentage as a decimal.
🔑 Key Points to Remember
- ✓Decimal point separates whole from fraction
- ✓% means per hundred: 75% = 75/100 = 0.75
- ✓To find X% of Y: (X/100) × Y
- ✓Percentage increase/decrease: (change ÷ original) × 100
- ✓Always convert % to decimal before calculating
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