You have a 3D array A with shape (4,1,5) and a 2D array B with shape (1,3). You want to add them using broadcasting. What will be the shape of the result?

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NumPy - Broadcasting

You have a 3D array A with shape (4,1,5) and a 2D array B with shape (1,3). You want to add them using broadcasting. What will be the shape of the result?

ABroadcasting will fail with ValueError

B(4, 1, 3)

C(1, 3, 5)

D(4, 3, 5)

Step-by-Step Solution

Solution:

Step 1: Align shapes by adding missing dimension
A shape is (4,1,5), B shape is (1,3). Treat B as (1,1,3) to match 3D shape.
Step 2: Compare dimensions right to left
For each dim: 5 vs 3 (A's last dim 5, B's last dim 3) - mismatch. This means broadcasting fails.
Step 3: Re-examine dimension matching
Actually, B's shape is (1,3), so when adding to A (4,1,5), B is broadcast to (1,1,3). Compare dims: 5 vs 3 (A's last dim 5, B's last dim 3) - mismatch. NumPy aligns shapes from right: A (4,1,5), B (1,1,3). Last dims 5 and 3 mismatch, so broadcasting fails.
Final Answer:
Broadcasting will fail with ValueError -> Option A
Quick Check:
Mismatch in last dims 5 and 3 causes failure [OK]

Quick Trick: Align dims right to left; mismatch without 1 causes error [OK]

Common Mistakes:

Assuming missing dims auto-align without prepending
Ignoring last dimension mismatch
Thinking broadcasting always works if dims differ

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More NumPy Quizzes

You have a 3D array A with shape (4,1,5) and a 2D array B with shape (1,3). You want to add them using broadcasting. What will be the shape of the result?

Step 1: Align shapes by adding missing dimension

Step 2: Compare dimensions right to left

Step 3: Re-examine dimension matching

Final Answer:

Quick Check:

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