Fireman B,Fireman C
Step-by-step explanation:
Let the rate of fireman A be [tex]r_{a}[/tex].
Let the rate of fireman B be [tex]r_{b}[/tex].
Let the rate of fireman C be [tex]r_{c}[/tex].
Rate of any fire man is defined as the ratio of number of rungs of ladder he climbed to the time he takes to climb them.
It is given that fireman A takes [tex]5[/tex] seconds for [tex]15[/tex] rungs.
[tex]r_{a}[/tex]=[tex]\frac{15}{5}=3[/tex].
It is given that fireman B takes [tex]6[/tex] seconds for [tex]12[/tex] rungs.
[tex]r_{a}[/tex]=[tex]\frac{12}{6}=2[/tex].
It is given that fireman C takes [tex]7[/tex] seconds for [tex]14[/tex] rungs.
[tex]r_{a}[/tex]=[tex]\frac{14}{7}=2[/tex].
It is evident from above data that fireman B,C climb ladder at the same rate.
