In this math problem, we will be using rate of change.
850 naira’s / 20 mangoes
= 42.5 nairas for one mango.
Next, to find the cost of 15 mangoes, we will take the cost of our one mango and simply multiply it by 15.
= 42.5 nairas * 15
= 637.50 nairas
So, in conclusion, the cost of 15 mangoes is 637.50 naira.
Answer:

Step-by-step explanation:
There aren't any factors that cancel (except 3x). The best you can do is multiply it out.

September
30-10=20 days
October 31
November 10
Time=20+31+10=61 days
A=42,000×(1+0.035÷365)^(61)
A=42,246.38
Interest earned
I=42,246.38−42,000
I=246.38