A1. We have two similar right triangles. The first one has legs measuring $3 \mathrm{~cm}$ and $4 \mathrm{~cm}$, while in the second one, the hypotenuse measures $10 \mathrm{~cm}$. The perimeter of the second triangle is
(A) $6 \mathrm{~cm}$
(B) $24 \mathrm{~cm}$
(C) $25 \mathrm{~cm}$
(D) $17 \mathrm{~cm}$
(E) none of the above
A1. The hypotenuse of the first right-angled triangle is $\sqrt{3^{2}+4^{2}}=5$, so the sides of the second triangle are twice as long. The perimeter of the second triangle is twice the perimeter of the first, thus $2(3+4+5)=$ $24 \mathrm{~cm}$.