Question

What is the value of the whole number N,if:N=1/2of2/3of3/4of4/5of100?

Answer 1

100/5 is 20/fifth so 4/5 of 100 is 80
80/4 is 20/quarter so 3/4 of 80 is 60
60/3 is 20/third so 2/3 of 60 is 40
40/2 is 20
 the answer is N=20

Answer 2

remember
(a/b) times (c/d)=(ac)/(bd) also
(ab)/c=(a/c)(b/c)
and
'of' means multiply

$( \frac{1}{2} )( \frac{2}{3} )( \frac{3}{4} )( \frac{4}{5} )( \frac{100}{1} )$=
$\frac{1*2*3*4*100}{1*2*3*4*5}$=
$( \frac{2*3*4}{2*3*4} )( \frac{100}{5} )$=
$(1)( \frac{100}{5} )$=
$\frac{100}{5}$=
$( \frac{5}{5} )( \frac{20}{1} )$=
$(1)( \frac{20}{1} )$=
20

answer is 20
or you can use bcalle's way and just cross multiply them