Mysql sum shows wrong answer for decimal type

Question

sales_id = 12
product_rate =
2090.00 making_charge = 83.60
handling_charge = 0.00

they are all decimal (10.2) types. My request

SELECT SUM( making_charge + product_rate + handling_charge ) AS tax_tourn
FROM  `sales_details` 
WHERE  `sales_id` =12

As a result, I get
 tax_tourn = 10784.40
which is not correct

2090.00 + 83.60 + 0.00 = 2173.60

why does mysql show the wrong answer?

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Details Recently Added

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I have two sales tables and sales_details. sales_id is the primary key for sales, and sales_details_id is the primary key for sales_details.
sales_id is the foreign key in sales_details.
In sales_details with the same sales_id, there may be multiple rows.

(sales_id= 12) .

Answer 1

1 , , where.

SELECT COUNT(*)
FROM  `sales_details` 
WHERE  `sales_id` =12

Answer 2

, , sales_id =12.