Question

The average temperature of Monday to Wednesday was ${37^{\circ}}C$ and from Tuesday to Thursday was ${34^{\circ}}C$.
If the temperature on Thursday was 4/5 of Monday, what was the temperature on Thursday.
A. ${36^{\circ}}C$
B. ${46^{\circ}}C$
C. ${56^{\circ}}C$
D. ${66^{\circ}}C$

Answer 1

Hint: In order to solve this question we will first find the combined temperature of Monday, Tuesday, and Wednesday and similarly the combined temperature of Tuesday, Wednesday, and Thursday then by subtracting them we will find the difference between Monday and Thursday as the temperature in Thursday is given 4/5 of the Monday so by subtracting Monday and 4/5th of the Monday will be equal to Thursday and temperature of Monday will be found. Hence by the relation, the temperature of Thursday will be found.

Complete step by step Solution:
For solving this question we will first find the combined temperature of Monday, Tuesday, and Wednesday, as the average temperature, is given to us, is ${37^{\circ}}C$ so the combined temperature of Monday, Tuesday, and Wednesday will be
$37 \times 3 = {111^{\circ}}C$
Now similarly the combined temperature of Tuesday, Wednesday, and Thursday as the average of these three days is given by ${34^{\circ}}C$ will be:
$34 \times 3 = {102^{\circ}}C$
Now the difference between the temperature between Monday and Thursday as two days Tuesday and Wednesday are common in both of them will be:
Monday (temperature) – Thursday (temperature) = 111 – 102
Monday (temperature) – Thursday (temperature) = 9 ……………………………. (1)
Now according to the question, it is given that:
$\dfrac{4}{5}$ Monday (temperature) = Thursday (temperature) …………………………..(2)
Putting the value of Thursday (temperature) in equation …(1) we get:
Monday (temperature) - $\dfrac{4}{5}$ Monday (temperature) = 9
On further solving:
Monday (temperature) / 5 = 9
On substituting the values another side:
Monday (temperature) = 45
Now putting the value Monday in the equation …. (2)
$\dfrac{4}{5} \times 45 = $ Thursday (temperature)
On further solving this we get:
Thursday (temperature) = ${36^{\circ}}C$

Hence the correct option will be A.

Note:
While solving these types of questions we should keep in mind separate questions about what are days covered by the combined temperature and what are the days eliminated when we are subtracting the temperature of some days.