\fdO'^ - Old Forge Coal Mines

178 ELEMENTARY MECHANICS.
(421) See Fig, 31. Since any number of quadrilaterals
can be drawn with the sides given, any number of answers
can be obtained.
Draw a quadrilateral, the lengths of whose sides are equal
to the distances between the weights, and locate a weight on
each corner. Apply formula 20 to find the distance C, IV^ ;
9 X 18
thus. C W. = 9 + 21
5.4". Measure the distance C, W^
Fig. 31.
suppose it equals say 36". Apply the formula again.
31.7'.
15 X 36
15 +(9 + 21)
= 12". Measure C, W^ ; it equals say
Apply the formula again. C^C ^ 17 X 31.7 = 8.7".
17 + 15 + 9 + 21
C is center of gravity of the combination.
(422) het A B C D E, Fig. 32, be the outline, the
right-angled triangle cut-off being E S D. Divide the
figure into two parts by the line ;« «, which is so drawn
that it cuts off an isosceles right-angled triangle m B n,
equal in area to E S D, from the opposite corner of the
square.