[tex]1 \ h = 60 \ min[/tex]
[tex]1 \ min = 60 \ s[/tex]
[tex]1 \ h = 60 \cdot 60 \ s = 3600 \ s[/tex]
[tex]a) \ 45 \ min=45:60 \ h=\dfrac{45}{60} \ h=\dfrac{45:15}{60:15} \ h=\boxed{\dfrac{3}{4} \ h }[/tex]
[tex]25 \ min = 25 :60 \ h=\dfrac{25}{60} \ h = \dfrac{25:5}{60:5} \ h=\boxed{\dfrac{5}{12} \ h }[/tex]
[tex]1\ s=1:3600 \ h=\boxed{\dfrac{1}{3600} \ h }[/tex]
[tex]15 \ s = 15:3600 \ h=\dfrac{15}{3600} \ h= \dfrac{15:15}{3600:15} \ h=\boxed{\dfrac{1}{240} \ h }[/tex]
[tex]1 \ km = 1000 \ m[/tex]
[tex]1 \ m = 100 \ cm[/tex]
[tex]1 \ km = 1000 \cdot 100 \ cm = 100000 \ cm[/tex]
[tex]b) \ 200 \ m = 200:1000 \ km = \dfrac{200}{1000} \ km=\dfrac{200:200}{1000:200} \ km=\boxed{\dfrac{1}{5} \ km }[/tex]
[tex]8 \ m = 8:1000 \ km=\dfrac{8}{1000} \ km=\dfrac{8:8}{1000:8} \ km= \boxed{\dfrac{1}{125}\ km }[/tex]
[tex]125 \ cm=125:100000 \ km=\dfrac{125}{100000} \ km=\dfrac{125:125}{100000:125} \ km=\boxed{\dfrac{1}{800} \ km }[/tex]
[tex]1500 \ cm=1500:100000 \ km=\dfrac{1500}{100000} \ km=\dfrac{1500:500}{100000:500}\ km=\boxed{\dfrac{3}{200} \ km }[/tex]