i-Ready Classroom Mathematics Grade 3, Unit 3: Addition Subtraction and Place Value

What is my child learning in Unit 3?

• Using place value to round, deciding whether 281 is closer to 200 or 300 by looking at the tens digit. Learn more: Rounding to the nearest 10 or 100
• Adding and subtracting three-digit numbers with methods like adding up, partial sums, and regrouping. Learn more about adding within 1,000: Adding within 1,000 · Learn more about subtracting within 1,000
• Solving two-step problems with three-digit numbers, and estimating first to see whether the exact answer is reasonable. Learn more: Story problems with two steps
• Finding patterns in addition tables, such as an even number plus an even number always being even, and explaining why. Learn more: Spotting patterns in times tables

How you can help

1. 1Ask your child to estimate a larger receipt total, like $38 and $24, by rounding each amount to the nearest ten dollars, then see how close the real total comes.
2. 2Ask how many pages are left when a 250-page book is open to page 138, and let your child explain how they worked it out (112).
3. 3Ask your child to add pairs of even house numbers on a walk, like 24 and 36, and say whether the sum is even or odd and why.

Where kids can get stuck

• Rounding 281 to 200 because the hundreds digit is 2, without checking the tens.
• Forgetting to add the regrouped tens and hundreds, so 367 + 245 comes out as 502 instead of 612.
• Trusting a pattern after two or three examples without checking whether it always works.

Practice makes perfect

Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.

Words your child will hear

round

To swap a number for the closest ten or hundred, like 47 to 50.

place value

What a digit is worth based on its place, like the 4 in 347 meaning 4 tens.

estimate

A smart guess close to the real answer, often found by rounding.

regroup

To trade between places, like turning 1 hundred into 10 tens to subtract.

partial sums

Adding the hundreds, tens, and ones separately, then adding those answers together.

sum

The total you get when you add.

difference

How much more or less one number is than another.

pattern

Something that repeats or changes by a rule we can describe.

even number

A number that can be split into two equal groups, like 8 = 4 + 4.