Answer:
The price of rice per gram is 0.006$
Step-by-step explanation:
I. David wants to make 10 servings,
each require 75 g of rice and 5 spice. When ratio is 15:1
If rice : spice = 75 : x
15x = 75
x = 5
=> 5 * 15 : 1 * 5
= 75 : 5
So rice : spice is 75 : 5
II. When 1 serving require 75 : 5
So 10 servings is 10 * 75 : 5 * 10
= 750 : 50
So he must has 750 grams rice and 50 grams spice.
III. He must buy spice and rice which..
a) He has 40 grams spice, he'll buy for 10 grams spice.
b) He has no rice, he'll buy for 750 grams rice.
But the question only ask for price of rice which he spend 4.5$
=
= 0.006$
In 1 gram of rice he spend 0.006$
If 750 grams of rice, he'll spend 750 * 0.006$ = 4.5$ => true
That makes 0.006$ is the right answer.
Hope that help :)
