5.NBT.6Find whole-number quotients of whole numbers with up to four-digit dividends and two-digit divisors, using strategies based on place value, the properties of operations, and/or the relationship between multiplication and division.
๐ฏLearning Objectives (SWBAT)
Divide multi-digit numbers by 1-digit divisors using the standard algorithm
Divide multi-digit numbers by 2-digit divisors using the standard algorithm
Use partial quotients as an alternative division strategy
Interpret remainders in context
๐ Real-World Division
Division is everywhere! Think about these situations:
๐
Pizza Party
You have 720 slices of pizza for 8 classes. How many slices does each class get?
๐ฆ
Packing Boxes
A warehouse has 2,634 items to pack into boxes of 5. How many full boxes?
๐ฐ
Saving Money
You earned $2,528 over 8 months. How much per month?
Today we'll master the tools to solve problems like these โ and bigger ones!
๐ Division Vocabulary
Dividend
The number being divided (the total amount)
In 63 รท 5, the dividend is 63
Divisor
The number you divide by (the group size)
In 63 รท 5, the divisor is 5
Quotient
The answer to a division problem
In 63 รท 5 = 12 r3, the quotient is 12
Remainder
The amount left over after dividing evenly
In 63 รท 5 = 12 r3, the remainder is 3
โจ The DMSBR Algorithm
Long division follows a repeating pattern. Remember these 5 steps:
๐ง Does McDonald's Sell Burgers Raw?
โ
D
Divide
โ๏ธ
M
Multiply
โ
S
Subtract
โฌ๏ธ
B
Bring Down
๐
R
Repeat
Repeat the cycle until there are no more digits to bring down!
๐ 1-Digit Division Steps
Follow DMSBR for each digit position, working left to right:
1
Divide
How many times does the divisor go into the current number? Write the digit above.
2
Multiply
Multiply the divisor by the quotient digit. Write the product below.
3
Subtract
Subtract the product from the current number. The difference must be less than the divisor.
4
Bring Down & Repeat
Bring down the next digit. Start the cycle again until no digits remain.
๐ก Check: Your remainder must always be LESS than the divisor!
What happens if you pick a quotient digit that's too big? Too small?
How do you check your answer when you're done?
๐ก Check strategy: Multiply your quotient ร divisor, then add the remainder. You should get back the dividend!
โจ 2-Digit Divisors
Dividing by 2-digit numbers uses the same DMSBR steps โ but the "Divide" step is harder!
โ
What's the Same
Same DMSBR cycle: Divide, Multiply, Subtract, Bring Down, Repeat
โก
What's Different
You need to estimate each quotient digit. Use compatible numbers to guess!
๐ Estimation Trick
Round the divisor to the nearest ten, then use that to estimate. For example: 43 rounds to 40, so for 43โ255, think "40 ร ? โ 255" โ try 6. Then check: 43 ร 6 = 258. Too big! Try 5: 43 ร 5 = 215. โ
๐ 2-Digit Division Steps
๐ Updated Procedure for 2-Digit Divisors
1
Estimate the quotient digit Round the divisor to the nearest ten. Use multiplication facts to estimate.
2
Multiply to check Multiply divisor ร your estimate. If the product is too big, try one less.
3
Subtract Subtract the product. The difference MUST be less than the divisor.
4
Bring Down & Repeat Bring down the next digit and start the cycle again.
โ๏ธ Problem 7
๐จโ๐ซ I Do โข 2-Digit Divisor
2,554 รท 43
Divide using the standard algorithm with estimation
Another way to divide! Instead of going digit by digit, subtract friendly chunks.
๐งฑ
The Big Idea
Subtract large, easy-to-multiply chunks from the dividend. Keep going until you can't subtract anymore!
โ
Add Up the Chunks
Each chunk is a "partial quotient." Add all the partial quotients together for your final answer!
๐ก Why Use Partial Quotients?
You get to choose your own "friendly" numbers! Use multiples of 10, 100, or whatever you're comfortable with. There's no wrong chunk โ just faster and slower paths!
๐ Partial Quotients Steps
๐ How to Use Partial Quotients
1
Pick a friendly chunk Ask: "How many groups of [divisor] can I easily take out?" Use multiples of 10 or 100.
2
Subtract the chunk Multiply divisor ร chunk, then subtract from what's left. Write the chunk to the side.
3
Repeat Keep subtracting chunks until the remaining amount is less than the divisor.
4
Add the partial quotients Add all your chunks together. That sum is your quotient! What's left over is the remainder.
โ๏ธ Problem 13
๐จโ๐ซ I Do โข Partial Quotients
4,587 รท 7
Solve using partial quotients โ subtract friendly chunks!
๐งฑPartial Quotients
1Start with 4,587. Take out 600 groups of 7: 7 ร 600 = 4,200. Subtract: 4,587 โ 4,200 = 387. Write 600 to the side.
2Now we have 387. Take out 50 groups of 7: 7 ร 50 = 350. Subtract: 387 โ 350 = 37. Write 50 to the side.
3Now we have 37. Take out 5 groups of 7: 7 ร 5 = 35. Subtract: 37 โ 35 = 2. Write 5 to the side. 2 < 7, so we stop.
3Bring down 8 โ 48. 8 into 48 โ 6. Multiply: 8 ร 6 = 48. Subtract: 48 โ 48 = 0. No remainder!
4Answer the question: They earned $316 per month. Check: $316 ร 8 = $2,528 โ
โ Answer
$2,528 รท 8 = $316 per month
๐ฌ Turn & Talk
๐ฃ๏ธPartner Discussion
Standard Algorithm vs. Partial Quotients
Which strategy do you like better? Why?
When might partial quotients be easier than the standard algorithm?
When might the standard algorithm be faster?
๐ก Both strategies give the same answer! The standard algorithm is usually faster once you master it. Partial quotients is great when you're still learning, or when the divisor is tricky.
๐ Key Takeaways
๐
DMSBR โ Divide, Multiply, Subtract, Bring Down, Repeat. This cycle is the heart of the standard algorithm.
๐ฏ
Estimation is key for 2-digit divisors. Round the divisor to the nearest 10 to help you estimate each quotient digit.
๐งฑ
Partial quotients is an alternative strategy. Subtract friendly chunks, then add them up at the end.
โ
Always check: your remainder must be less than the divisor. Verify with multiplication: quotient ร divisor + remainder = dividend.
๐ซ Exit Ticket
Solve these on your own. Show your work!
Problem 1
6,453 รท 9
1-digit divisor
Problem 2
1,748 รท 23
2-digit divisor
Problem 3
4,235 รท 8
Choose any method!
๐ Answers: (1) 717 R0 | (2) 76 R0 | (3) 529 R3
Great Work! ๐
You now have THREE powerful division strategies in your toolbox!