Rounding and Approximation

Methods of Rounding Decimal Places Identify the digit of the decimal place required  Look at the next digit to the right  If this digit is 5 or more round up the required decimal place

Examples Ex Round to 2 decimal places 2 nd decimal place is the 4 i.e 2 places after the decimal point The next number to the right is a 6 So round up becomes 5.35 to 2 decimal places

Examples Ex Round to 1 decimal place 1st decimal place is the 3 i.e 1 place after the decimal point The next number to the right is a 4 So Don`t round up becomes 5.3 to 1 decimal places

Questions to 1d.p to 2d.p to 3d.p to 2d.p to 1d.p

Methods of Rounding Significant Figures Identify the digit of the significant figure required. This means start counting from the first non zero digit  Look at the next digit to the right  If this digit is 5 or more round up the required significant figure

Examples Ex Round to 2 significant figures 2 nd significant figure from the start is the 3 The next number to the right is a 4 So Don`t round up becomes 5.3 to 2 significant figures

Examples Ex Round to 3 significant figures 3rd significant figure is the 4 i.e 3 places from the start The next number to the right is a 6 So round up becomes 5.35 to 3 significant figures

Examples Ex Round to 1 significant figures 1st significant figure is the 2 i.e 1 place from the start The next number to the right is a 5 So round up but remember the answer must be 30 not 3 as the original number is closer to 30 than becomes 30 to 1 significant figures

Questions to 1s.f to 2s.f to 3s.f to 4s.f to 1s.f

Notes

Methods of Rounding Decimal Places Identify the digit of the decimal place required Look at the next digit to the right If this digit is 5 or more round up the required decimal place Ex Round to 2 decimal places 2 nd decimal place is the 4 i.e 2 places after the decimal point The next number to the right is a 6 So round up becomes 5.35 to 2 decimal places

Significant Figures Identify the digit of the significant figure required. This means start counting from the first non zero digit Look at the next digit to the right If this digit is 5 or more round up the required significant figure Ex Round to 3 significant figures 3 rd significant figure from the start is the 4 The next number to the right is a 6 So round up becomes 5.35 to 3 significant figures