Adding and Subtracting Decimals

The secret to adding and subtracting decimals is all about lining things up properly - think of it like parking cars in designated spaces! You need to make sure the decimal points sit directly under each other, with units under units and tenths under tenths.

When you're adding numbers like 3.42 + 1.7, don't panic about the different lengths. Simply add a zero to make 1.7 become 1.70 - this makes the calculation much clearer. Your sum becomes 3.42 + 1.70 = 5.12, and you're sorted!

Subtraction works exactly the same way - line up those decimal points first. For 7.43 - 2.59, you might need to borrow from the column to the left, just like with whole numbers. Remember, if one number has fewer decimal places, add zeros to match the other number's length.

Top Tip: Always double-check your decimal point alignment before you start calculating - it's the most common mistake students make!

Multiplying, Dividing and Converting Decimals

Multiplying decimals is simpler than you think - just ignore the decimal points completely at first! Multiply the numbers as if they were whole numbers, then count up all the decimal places in both original numbers. Your final answer needs exactly that many decimal places.

For example, 4.5 × 2.4 becomes 45 × 24 = 1080. Since you had one decimal place in each number (that's 2 total), your answer is 10.8. Easy!

Dividing decimals requires a clever trick - turn the division into a fraction first. Then multiply both the top and bottom by 10, 100, or 1000 until you've eliminated all decimal points. So 5.4 ÷ 0.06 becomes 540 ÷ 6 = 90.

When converting between fractions, decimals and percentages, remember the simple rules: multiply by 100 to go from decimal to percentage, divide by 100 to go the other way. For fractions, divide the top by the bottom to get a decimal.

Remember: Practice makes perfect - try these techniques with your pocket money calculations to see decimals in action!