Find the area of right-angled triangles with legs: a) 6cm and 22mm. b) 38mm and 72mm.

Brief notation of the problem condition:
Rectangular ∆;
a) a = 6 cm; b = 22 mm .;
b) a = 38 mm; b = 72 mm .;
S∆ =?
Solution:
The area of a right-angled triangle is half the product of its legs.
S∆ = (1/2) ab,
where a and b are the legs of a right-angled triangle.
a) Let us reduce all lengths to one unit of measurement.
If 1 cm = 10 mm, then 6 cm = 60 mm.
S∆ = 60 * 22 = 1 320 (mm²);
b) S∆ = 38 * 72 = 2 736 (mm²);
Answer: a) 1 320 mm²; b) 2 736 mm².