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^@` ?

Answer

C

Explanation

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