Lesson 4: Write and Evaluate Numerical Expressions with Exponents6.AT.6c

I can…

I can write numerical expressions from a real situation and evaluate them using the order of operations, including powers.

Key words

• Write and Evaluate Numerical Expressions with Exponents — Write a number phrase with powers, then find its value.
• Numerical expression — A math phrase with numbers and signs, but no letters.
• Evaluate — Find the value by putting in numbers for the letters.
• Order of operations — Do ( ) first, powers next, then × and ÷, then + and −, left to right.
• Power — A short way to write 2 × 2 × 2 as 2³.
• Base — The number in a power that repeats: the 2 in 2³.
• Exponent — A small raised number. It counts the times a number is used.
• Grouping symbols — Marks like ( ) that tell you what to do first.

Steps

1. Sofia buys 2 member tickets at $15, 4 non-member tickets at $20, and 8 student tickets at $2 each. I write one expression for each ticket type: 2 × 15, 4 × 20, and 8 × 2.
2. The whole order is the three costs added together: 2 × 15 + 4 × 20 + 8 × 2.
3. Now I evaluate. There are no grouping symbols and no powers yet, so multiplication comes first, left to right: 30 + 80 + 16.
4. Then I add: 30 + 80 + 16 = 126. The tickets cost $126.

Try it

A family buys 5 movie tickets at $10 each and 4 snacks that cost 3² dollars each. Evaluate 5 × 10 + 4 × 3² to find the total cost in dollars.

Check your answer

86

Powers first: 3² = 9. Then multiply left to right: 5 × 10 = 50 and 4 × 9 = 36. Then add: 50 + 36 = 86.

Sentence starter

I know ___ because ___.

Goal: I can explain my steps using the words expression, evaluate, order of operations, base, and exponent.