Why my code doesn't meet all the testcases ??

Question

Here is the problem:

You are getting ready to paint a piece of art. The canvas and brushes that you want to use will cost 40.00. Each color of paint that you buy is an additional 5.00. Determine how much money you will need based on the number of colors that you want to buy if tax at this store is 10%.

Task
Given the total number of colors of paint that you need, calculate and output the total cost of your project rounded up to the nearest whole number.

Input Format
An integer that represents the number of colors that you want to purchase for your project.

Output Format
A number that represents the cost of your purchase rounded up to the nearest whole number.

Sample Input
10

Sample Output
99

Here is my code:

canva_brush = 40
color_num = int(input())
color_price = color_num * 5
first_total = canva_brush + color_price
total = int(first_total + (first_total *(10/100)))
print(round(total))

There are two test cases that make my code fail and I don't know why??

Answer 1

rounded up.

round does not always round up.
https://www.geeksforgeeks.org/round-function-JUMP_LINK__&&__python__&&__JUMP_LINK/

check out math.ceil
https://www.w3schools.com/python/ref_math_ceil.asp

Answer 2

you're converting to int before applying math.ceil. Don't do that. It truncates the float, so you're giving math.ceil the wrong value. round, math.ceil and math.floor needs float, not int. Sorry, I shoul have noticed that error in your code earlier.

https://codedamn.com/news/JUMP_LINK__&&__python__&&__JUMP_LINK/converting-float-to-int-in-python

total = first_total + (first_total*(10/100))
print(math.ceil(total))

--edit--
Thanks for the clarification by Jan, this is actually a wrong solution. Use round, not math.ceil. Just don't convert to int before rounding.
But I still believe that the code coach was misleading in it's use of the term "rounded up".

Answer 3

Unfortunately also math.ceil gave me an error😭

Answer 4

It's 5 * input + 40, and then you divide it with 10 and use the normal round and not math.ceil or math.floor.

Answer 5

Jan
you're right. my mistake...😅

It turns out it is wrong to use math.ceil.

The wording threw me off.

"rounded up"

It should have been

"rounded to"

Now I feel that the wording of the code coach problem is misleading....

but yes, the int conversion was the source of yasminsherif's error, not the use of round.

why "rounded up" is a bad choice of words in the Code Coach:

import math

print(f'{math.ceil(1.5) = }', 'rounded up')
print(f'{round(1.5) = }', 'rounded up')
print(f'{math.floor(1.5) = }', 'rounded down')
print()
print(f'{math.ceil(2.5) = }', 'rounded up')
print(f'{round(2.5) = }', 'rounded down <--!!')
print(f'{math.floor(2.5) = }', 'rounded down')