Question

answer this properly in a procedure..................................................

Answer 1

(1) if two quantities x and y vary directly with each other , then ratio of their corresponding values remains constant.

actually, x is directly proportional to y means, x = ky
where k is constant. hence, k = x/y , e.g., ratio of x and y of its corresponding values remains constant.

(2) we know,
       perimeter of circle = 2πr , where r is the radius of circle.
or, perimeter of circle = π(2r) = π*diameter of circle.
here you know, π = 3.14 is always constant.
hence, perimeter of circle is directly proportional to diameter of circle.

answer is directly

(3) car is travelling  48 km in one hour ,
it means speed of car = 48km/h
time given = 12minutes. = 12/60 hr = 1/5 hr
we know,
       distance = speed * time = 48*1/5 km = 9.6 km
answer is 9.6km

(4) thickness of a pile of 12 cardboard sheets = 45mm
so, thickness of a pile of 1 cardboard sheets = 45mm/12
so, thickness of a pile of 240 cardboard sheets = 45mm*240/12 = 900mm
= 900/10 cm = 90 cm [1cm = 10mm]
answer is 90cm

(5)in direct proportion,
  a₁/b₁ = a₂/b₂  because in direct proportional means , a/b = k
it means , a₁/b₁ =a₂/b₂ =a₃/b₃ =....... = k (always constant)

answer is ' = '