Step-by-step explanation:
the x-axis is Celsius, the y-axis is Fahrenheit.
so, for a) you find 20 on the C axis, and then follow that grid line straight up until you hit line. from there you follow the grid line straight to the left until you hit the F axis, and you count what value is there.
the same for 35.
and you will find 20 C = 68 F.
and 35 C = 95 F.
for b) you do the same but in the opposite direction. you start on the F axis, go right to the line and then down to the C axis and read that value there.
and you will find 50 F = 19 C
and 104 F = 40 C
c) is ready to find. at what F value his the line the F (or y) axis ?
look closely, and you will find it is at F = y = 32.
there you have also the old wisdom 0 C = 32 F.
the freezing point of water is at 0 C (on purpose, that was one of the reasons how and why the Celsius scale was created) and at 32 F (which nobody ever truly understood, why this was defined that way).
d) the gradient or slope of the line is always y/x indicating how many units y changes, when x changes a certain number of units when going from one point to another.
so, we have e.g. the points (0, 32) and (20, 68)
going from the first to the second point x changes 20 units (from 0 to 20), and y changes 36 units (from 32 to 68).
so the slope is 36/20 = 18/10 = 9/5
the general equation for a line is
y = ax + b
a = slope
b = y-intercept value
y is in our case F
x is in our case C
therefore, we have
F = 9/5 × C + 32
