In place values the places of ones and tens are must be explained. Numbers from 1 to 9 are single digit numbers when ‘nine and one more is makes a group of ten.Numbers from 11-20, such as number 11 have two digits and each digit is in a different place value. The left digit is the tens place and in 11 there are 1 tens. The right digit or last digit is the ones place and there are 1 ones. Therefore there are 1 tens plus 1 ones equals to 11