The steam point and the ice point of a mercury thermometer are marked as `80^@ and 10^@`. At what temperature on centigrade scale the reading of this thermometer will be `59^@` ?

Options

A. `70^(@)C`
B. `60^(@)C`
C. `40^(@)C`
D. `50^(@)C`

Answer

A

Explanation

Let the relation between the thermometer reading and centigrade by y= ax +b.
Given, at x = 100, y = 80 and at x = 0, y = 10
`therefore" "80 = 100a + b, 10=b rArr a = 0.7`
Now, we have to find x when y = 59
`therefore" "59= 100a +b, rArrx=70`
`therefore` The answer id `70^(@)C.`