From the following table, find the values of a, b and c:

Number of men	130	70	b	120
Number of days required to do the same work	a	39	30	c

It is a case of inverse variation:

∴ 130 x a = 70 x 39 = b x 30 = 120 x c

Taking,

130 x a = 70 x 39

⇒ a = $\dfrac{70 \times 39}{130}$

⇒ a = 7 x 3

⇒ a = 21

Taking,

70 x 39 = b x 30

⇒ b = $\dfrac{70 \times 39}{30}$

⇒ b = 7 x 13

⇒ b = 91

Taking,

70 x 39 = 120 x c

⇒ c = $\dfrac{70 \times 39}{120}$

⇒ c = 22.75

Hence, the value of a = 21, b = 91 and c = 22.75