Estimate $99+61$99+61.
Round both numbers to the nearest $10$10.
$\editable{}+\editable{}$+
Calculate the estimate.
Estimate $63-22$63−22.
Estimate $898-132$898−132.
Estimate $765+171$765+171.
use leading digit approximation to obtain estimates of calculations
check results of calculations for accuracy
ascertain the reasonableness of answers, in terms of context, to arithmetic calculations
apply approximation strategies for calculations if appropriate
use mental and/or flexible written strategies when appropriate