1) 1/ 3 ÷ 1 /9 = 1 /3 × 9/ 1 = 1·9/3·1 = 9/ 3 = 3 · 3 /3 = 3 = 3
2)3/ 8 ÷ 1 /2 = 3 /8 × 2/ 1 = 3·2 /8·1 = 6/ 8 = 3 · 2/ 4 · 2 = 3/ 4 = 0.75
3)4 /9 ÷ 8 /9 = 4 /9 × 9/ 8 = 4·9/ 9·8 = 36 /72 = 1 · 36 /2 · 36 = 1 /2 = 0.5
4)1 /12 ÷ 1/ 6 = 1/ 12 × 6/ 1 = 1·6/ 12·1 = 6 /12 = 1 · 6 /2 · 6 = 1 /2 = 0.5
5)3 /5 ÷ 1 /25 = 3 /5 × 25/ 1 = 3·25/ 5·1 = 75/ 5 = 15 · 5/ 5 = 15
6)2 /7 ÷ 3 /7 = 2 /7 × 7 /3 = 2·7 /7·3 = 14/ 21 = 2 · 7 /3 · 7 = 2 /3
7)1 /10 ÷ 1 /10 = 1 /10 × 10/ 1 = 1·10/ 10·1 = 10/ 10 = 1
8)3 /4 ÷ 5 /8 = 3 /4 × 8 /5 = 3·8 /4·5 = 24 /20 = 6 · 4/ 5 · 4 = 6/ 5 = 1·5 + 1 /5 = 1 / 1 5 = 1.2
всё)
NK=B-25
KM=4*NK=4*(B-25)
P=MN+NK+NK и P=67 ⇒ MN+NK+NK =67
MN+NK+NK =B+(B-25)+4*(B-25)=6B-125 ⇒
6B-125=67
6B=67+125
6B=192
B=192:6
B=32
отсюда
MN=B=32см
NK=B-25=32-25=7см
KM=4*(B-25)=4*7=28см