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Anchor Chart - Multiplying Decimals
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place value still rules
Anchor Chart · Grade 5 · 5.NBT.B.7
Multiplying Decimals
4 × 1.42
1
Break Apart by Place
1.42 =
1
+
0.4
+
0.02
4 ×
1
= 4 · 4 ×
0.4
= 1.6 · 4 ×
0.02
= 0.08
4 + 1.6 + 0.08 = 5.68
Four groups of each place, then add - same idea as whole numbers.
2
Area Model
4
1
0.4
0.02
4 × 1
4
4 × 0.4
1.6
4 × 0.02
0.08
4 + 1.6 + 0.08 =
5.68
Each place gets its own room - the tiny pieces stay visible.
3
The Algorithm, to Check
1.42
× 4
5.68
Multiply as if it were
142 × 4 = 568
.
1.42 has
two
decimal places, so the product gets
two
: 5.68.
Count decimal places at the end - the model explains
why
it lands there.
4
Estimate to Catch Mistakes
1.42 is close to 1½ → 4 × 1½ = 6
5.68 is near 6 ✓
A misplaced point screams: 56.8 or 0.568 are nowhere near 6.
The estimate is the answer's bodyguard.
