Wyoming Math 3.OA.8

3.OA.8 is a cluster heading. These are the individual standards under it.

• 3.OA.8a

  Represent these problems using equations with a symbol standing for the unknown quantity.

• 3.OA.8b

  Assess the reasonableness of answers using mental computation and estimation strategies including rounding.

01

What Students Need to Do

Students solve two-step stories with whole numbers and write an equation with a letter for the unknown. They multiply or divide before adding or subtracting when there are no parentheses, then estimate to check the answer.

02

What Mastery Looks Like

Given three packs of 19 pencils with eight given away, a student writes p = 3 × 19 − 8 and finds 49 pencils. They round 19 to 20 and eight to 10 to check that about 50 makes sense.

03

Common Misconceptions

Students may work left to right in 6 + 3 × 4 and get 36 instead of 18. They may leave out parentheses when a story calls for subtraction before multiplication, or use a letter as a unit label instead of an unknown. Some accept 90 pencils left after starting with 76 and giving some away.

04

How to Assess It

Exit ticket: Four boxes hold 19 pencils each, and 15 pencils are used. Write an equation with a letter for pencils left, solve it, and use rounding to check.

1. 01

   Put six counters in each of four paper cups, remove five, and have students write and solve an equation for counters left.

2. 02

   Have partners write a story for 6 + 3 × 4 and another for (6 + 3) × 4, then explain the difference.

3. 03

   Give pairs story cards and equation cards for 3 × 18 − 7, 3 × 18 + 7, and 3 × (18 − 7); race to match them.

4. 04

   Show a field trip sheet with four buses of 24 seats each and 18 empty seats; students find occupied seats and check by rounding.

• 6.EE.2c

  Use Order of Operations to evaluate algebraic expressions using positive rational numbers and whole-number exponents. Include expressions that arise from formul...

• 4.OA.3

  Solve multi-step word problems posed with whole numbers, including problems in which remainders must be interpreted.

• 1.OA.1

  Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, wit...

• 2.OA.1

  Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart,...