Question Video: Adding Two-Digit Numbers to Two-Digit Numbers without Regrouping Mathematics • 2nd Grade

Chloe spilled ink on her homework. Find the covered numbers.

03:05

Video Transcript

Chloe spilled ink on her homework. Find the covered numbers.

Chloe’s first sum is 28 plus another two-digit number. 28 plus something equals 89. And we can see that Chloe has spilled ink on one of the digits in her calculation. If we start by adding the ones, eight ones plus one one gives us a total of nine ones. What did Chloe add to her two 10s to give her a total of eight 10s? We know that two 10s plus six 10s gives us a total of eight 10s because two plus six is eight. So the missing digit in the tens column is a six. 28 plus 61 equals 89.

Chloe’s second sum has ink spilled on one of the ones digits. Thirty something plus 23 equals 58. So we just need to find the missing ones digit. What do we add to three to give us a total of eight? We know that three plus five equals eight. 35 plus 23 equals 58. So the missing digit is a five. Five ones plus three ones equals eight ones.

In Chloe’s last sum, two of the digits have been covered with ink. 64 plus what equals 79. Let’s start by thinking about the missing ones digit. 64 has four ones, and we have a total of nine ones. What do we need to add to four to give us nine ones? We know that four plus five is nine. So the missing ones digit is a five. Now let’s find the missing tens digit. 64 has six 10s, and we have a total of seven 10s. Six plus one equals seven. So the missing tens digit is a one. Six 10s plus one 10 equals seven 10s. So the missing number in this calculation is 15. 64 plus 15 equals 79.

We used the column addition method to help us find the missing digits. The missing number in the first addition is six, the second missing number is five, and the third missing number is 15.

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