Final answer:
The numbers 0.21 and 0.210 are equal because trailing zeros after the decimal point in a number do not change its value. The additional zero in 0.210 does not affect its value.
Step-by-step explanation:
When comparing the numbers 0.21 and 0.210, it is important to understand the concept of place value in decimal numbers. Both numbers have a tenths place and a hundredths place. The number 0.21 has a 2 in the tenths place and a 1 in the hundredths place. The number 0.210 also has a 2 in the tenths place, a 1 in the hundredths place, and a 0 in the thousandths place.
The presence of a zero in the thousandths place does not change the value of the number. Therefore, the numbers 0.21 and 0.210 are actually equal in value. This is because trailing zeros after the decimal point do not affect the value of a decimal number.