1)
3/4 * 4/5 = 3/5
1/4 + 3/5 = 5/20 + 12/20 = 17/20
1 - 17/20 = 3/20
2)
en 2001: 1 - 1/4 = 3/4
en 2002: 3/4 - 4/5 * 3/4 = 3/4 - 3/5 = 3/20
a) il reste 3/4 en 2001, il reste 3/20 en 2002, donc
3/4 - 3/20 = 12/20
b) 3/20
c) 3/20 = 6 ha, donc
20/20 = x ha
x = 6/(3/20) = 6*(20/3) = 40 ha...