Question

three - digit numbers
prerequisite: add two - digit numbers
study the example showing how to add
two - digit numbers. then solve problems 1 - 7.
example
find $27 + 16$.
you can add tens
and add ones.
$27 = 20 + 7$
$16 = 10 + 6$
\underline{\quad\quad\quad\quad\quad\quad}
$30 + 13 = 43$
(there are some block - diagram representations of the addition process here, showing 2 tens 7 ones, 1 ten 6 ones, and then 3 tens 13 ones)
there are 48 red grapes and 24 green
grapes in a salad.
1 write the tens and ones.
$48 = \underline{\quad\quad} + \underline{\quad\quad}$
$24 = \underline{\quad\quad} + \underline{\quad\quad}$
2 add the tens. then add the ones.
$\underline{\quad\quad} + \underline{\quad\quad} = 60$
$\underline{\quad\quad} + \underline{\quad\quad} = 12$
3 show how to find how many grapes
there are in all.
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on 13 add th
mbers 129

Explanation:

Problem 1

Step1: Decompose 48 into tens and ones

A two - digit number is made up of tens and ones. For 48, the tens digit is 4, which represents 4 tens or 40, and the ones digit is 8, which represents 8 ones. So \(48 = 40+8\).

Step2: Decompose 24 into tens and ones

For 24, the tens digit is 2, representing 2 tens or 20, and the ones digit is 4, representing 4 ones. So \(24=20 + 4\).

Step1: Add the tens

From the decomposition in problem 1, the tens parts of 48 and 24 are 40 and 20 respectively. So \(40 + 20=60\).

Step2: Add the ones

The ones parts of 48 and 24 are 8 and 4 respectively. So \(8+4 = 12\).

Step1: Recall the method

We can use the method of adding the tens sum and the ones sum together. From problem 2, we know that the sum of the tens is 60 and the sum of the ones is 12.

Step2: Calculate the total

To find the total number of grapes, we add these two sums: \(60+12 = 72\). We can also verify this by directly adding 48 and 24: \(48+24=(40 + 8)+(20+4)=(40 + 20)+(8 + 4)=60+12 = 72\).

Answer:

\(48=\boldsymbol{40}+\boldsymbol{8}\)
\(24=\boldsymbol{20}+\boldsymbol{4}\)

Problem 2