Adding Hundredths
Semester 4B · Chapter 13 · Lesson 4 · MATH-4B-C13-L04
Before you begin: prerequisite check
Recall: 12.03–12.04; 13.02. Attempt these questions independently first.
Calculate 4.4 − 1.9.
Show answer and reasoning
Rename 4.4 as 3 wholes and 14 tenths. Subtract 1 whole and 9 tenths; result 2.5.
Calculate 2.1 − 1.5.
Show answer and reasoning
Rename 2.1 as 1 wholes and 11 tenths. Subtract 1 whole and 5 tenths; result 0.6.
Calculate 5.2 − 1.5.
Show answer and reasoning
Rename 5.2 as 4 wholes and 12 tenths. Subtract 1 whole and 5 tenths; result 3.7.
Key vocabulary
- decimal point
- separator between whole units and fractional place values
- regroup
- exchange equivalent place-value units
- hundredth
- one hundredth of a whole
- exact amount
- quantity without rounding
Understand the concept
Add hundredths to hundredths and tenths to tenths. For 1.78+0.65, line up place values: eight hundredths plus five hundredths gives thirteen hundredths, so exchange ten of them for one tenth. Then seven tenths plus six tenths plus the exchanged tenth gives fourteen tenths, requiring one more exchange. The result is 2.43. Write 0.6 as 0.60 when needed. A 10-by-10 grid or money model can show the exchanges.
Fully worked examples and immediate checks
Read each example, predict how to begin, then follow its numerical explanation. The check below it is a fresh problem.
Worked example 1
Calculate 1.59 + 1.65.
Add 159+165 exact hundredths = 324 hundredths = 3.24.
Check 1: try it yourself
Calculate 3.40 + 3.91.
Show answer and reasoning
Add 340+391 exact hundredths = 731 hundredths = 7.31.
Worked example 2
Calculate 2.34 + 3.10.
Add 234+310 exact hundredths = 544 hundredths = 5.44.
Check 2: try it yourself
Calculate 5.71 + 2.49.
Show answer and reasoning
Add 571+249 exact hundredths = 820 hundredths = 8.20.
Worked example 3
Calculate 4.48 + 1.89.
Add 448+189 exact hundredths = 637 hundredths = 6.37.
Check 3: try it yourself
Calculate 3.88 + 2.64.
Show answer and reasoning
Add 388+264 exact hundredths = 652 hundredths = 6.52.
Guided practice
Calculate 7.50 + 2.66.
Show answer and reasoning
Add 750+266 exact hundredths = 1016 hundredths = 10.16.
Calculate 5.90 + 3.38.
Show answer and reasoning
Add 590+338 exact hundredths = 928 hundredths = 9.28.
Calculate 3.37 + 2.22.
Show answer and reasoning
Add 337+222 exact hundredths = 559 hundredths = 5.59.
Calculate 4.16 + 1.58.
Show answer and reasoning
Add 416+158 exact hundredths = 574 hundredths = 5.74.
Calculate 2.49 + 1.94.
Show answer and reasoning
Add 249+194 exact hundredths = 443 hundredths = 4.43.
Independent practice
Calculate 1.65 + 3.07.
Show answer and reasoning
Add 165+307 exact hundredths = 472 hundredths = 4.72.
Calculate 3.67 + 3.44.
Show answer and reasoning
Add 367+344 exact hundredths = 711 hundredths = 7.11.
Calculate 1.97 + 3.50.
Show answer and reasoning
Add 197+350 exact hundredths = 547 hundredths = 5.47.
Calculate 5.10 + 3.97.
Show answer and reasoning
Add 510+397 exact hundredths = 907 hundredths = 9.07.
Calculate 2.82 + 1.86.
Show answer and reasoning
Add 282+186 exact hundredths = 468 hundredths = 4.68.
Calculate 7.81 + 3.80.
Show answer and reasoning
Add 781+380 exact hundredths = 1161 hundredths = 11.61.
Calculate 3.39 + 3.32.
Show answer and reasoning
Add 339+332 exact hundredths = 671 hundredths = 6.71.
Calculate 6.13 + 3.43.
Show answer and reasoning
Add 613+343 exact hundredths = 956 hundredths = 9.56.
Challenge and transfer
Use a diagram or verbal justification where appropriate. The goal is transfer rather than speed.
Calculate 7.63 + 3.76. Explain how place value or a model can check your result.
Show answer and reasoning
Add 763+376 exact hundredths = 1139 hundredths = 11.39. A correct explanation should name the relevant fractional place values and verify the answer.
A learner claims: “0.4 + 0.35 = 0.39.” Identify what is wrong or incomplete and give a mathematically correct explanation.
Show answer and reasoning
False: 0.40 + 0.35 = 0.75; align hundredths with hundredths. Explain the relevant quantities or properties, not merely the final answer.
Exit check
Calculate 2.98 + 2.62.
Show answer and reasoning
Add 298+262 exact hundredths = 560 hundredths = 5.60.
Calculate 5.68 + 1.99.
Show answer and reasoning
Add 568+199 exact hundredths = 767 hundredths = 7.67.
Calculate 3.41 + 2.59.
Show answer and reasoning
Add 341+259 exact hundredths = 600 hundredths = 6.00.
Mastery check: Solve a new instance without hints, explain why the method works, and return later to confirm retention.