Estimate 61.3 to the nearest whole number.

To estimate 61.3 to the nearest whole number, we focus on the decimal portion of the number, which is 0.3 in this case. When rounding, the common rule is to look at the first digit after the decimal point. If this digit is less than 5, we round down to the nearest whole number; if it is 5 or greater, we round up.

In this instance, since the decimal is 0.3, which is less than 5, we round down. Therefore, we take the whole number part of 61.3, which is 61, and do not increase it. This makes 61 the nearest whole number estimation.

Choices that suggest 60, 62, or 63 are not appropriate in this case because they do not follow the rounding rule applied to decimals less than 5. Hence, the estimation of 61.3 to the nearest whole number is indeed 61.