<span>1
2</span>=1÷2⋅100=0.5⋅100=50<span>%
</span><span><span>1
4</span>=1÷4⋅100=0.25⋅100=25%
</span><span>
</span><span>1
5</span>=1÷5⋅100=0.2⋅100=20<span>%
</span><span>
</span><span>1
10</span>=1÷10⋅100=0.1⋅100=10<span>%
</span>
<span><span>1
20</span>=1÷20⋅100=0.05⋅100=5%
</span>
<span><span>1
25</span>=1÷25⋅100=0.04⋅100=4%
</span>
<span><span>1
50</span>=1÷50⋅100=0.02⋅100=2%
б)</span><span><span>2
4</span>=2÷4⋅100 =0.5⋅100=50%
</span><span><span>2
5</span>=2÷5⋅100 =0.4⋅100=40%
</span><span><span>7
10</span>=7÷10⋅100=0.7⋅100=70%
</span><span><span>9
20</span>=9÷20⋅100=0.45⋅100=45%</span><span>
</span>
Вот так. Надо делать. Просто дм перевести в см
4*1 7/12=4*19/12=19/3=5 4/3
(-2 5/21)*3=-47/21*3=-47/7=-6 5/7
-7 1/8 :(-3)=-7/8*(-1/3)=19/8=2 3/8
3 2/5*(-15)=17/5*(-15)=-51
Ответ таков, пиши: Р=(13+17)*2=60 (мм)