Answer:
£191.36
Step-by-step explanation:
Sum the parts of the ratio, 1 + 4 = 5 parts
Divide 320 by 5 to find the value of one part of the ratio.
320 ÷ 5 = 64 ← value of 1 part of the ratio , thus
4 parts = 4 × 64 = 256
Thus he bought 64 first class and 256 second class.
Cost = (64 × £0.67) + (256 × £0.58)
= £42.88 + 148.48
= £191.36
Answer:

Step-by-step explanation:
First, note that

And using the chain rule in one variable

Now remember that the chain rule in several variables sates that

Therefore the chain rule in several variables would look like this.

Answer:
$4.05
Step-by-step explanation:
45 x 9 = 4.05
X = 7. 7 x 4 = 28 and 28 + 3 = 31.
31>27