△m′n′p′ is the image of △mnp under a dilation through point c. mp=10 and m′p′=4 .
what scale factor was used in the dilation?
−2.5
−0.4
0.4
2.5

Divide the new length M'P' over the old one MP

(M'P')/(MP) = 4/10 = 0.4

The scale factor is 0.4

Because the scale factor is less than 1, it indicates the image (aka new figure) is smaller than the preimage (aka original figure). Basically the figure has been scaled down.