Decimal Numbers In Year Five children should know the place value of figures in decimal numbers to two places - tenths and hundredths - and also be capable of doing some adding and subtracting with decimals. They should also be confident when rounding decimal numbers up or down, and be familiar with sums involving decimal measurements such as metres/cm or £/pence. Decimal numbers are those that are smaller than a unit and are written after a decimal point. Decimal numbers are an alternative way of writing fractions. A quarter of a pizza written as a fraction would be 1⁄4, but written as a decimal would be 0.25. 0.25 is a decimal with two places - the 2 represents 2 tenths and the 5 is 5 hundredths.