Goals By the end of the lesson or a series of similar lessons, students will be able to count fluently by 10s from any given number 10-90, mentally add 10 or subtract 10 from any number 10-99, adding or subtracting 10 from any given number to solve story problems. Later in the year, this lesson can be used to help students to count fluently by 10s from any given number to 999, count fluently backwards by 10s from any given number to 999, count fluently by 100s from any given number to 999, count fluently by 100s backwards from any given number to 999.