Answer:
1/2
Step-by-step explanation:
If B is a dilation of figure A, the length of a given side in B will be equal to the scale factor times the corresponding side in A.
So, if 10 in figure A is corresponding to 5 in figure B, we get:
5 = k(10)
Where k is the scale factor.
Then, solving for k, we get:
5/10 = k(10)/10
1/2 = k
Therefore, the scale factor in the dilation is 1/2.
We can also say that B is smaller than A, so the scale factor should be a number lower than 1. Since 5 is half 10, we can say that the scale factor is one-half or 1/2.