How to directly judge the error of Double in decimal computation?

sources of topics and their own ideas

it is known that most small numbers cannot be fully represented in Double, and there will be errors when counting decimals.
is it equal to another decimal if there is an error-free error in quickly determining the number of small numbers by using the traditional method?
if you need to do the calculation by hand, how can you determine whether an advance is required when you change the number of characters into binary to 53 digits?
found that .net seems to use 40%, 60%, 50%. How can this rule be implemented in binary system?

related codes

/ / Please paste the code text below (do not replace the code with pictures)

the answers to the following questions are C and D
v2-c4f43ae4d680651f78488df070b09ae5_b.png

, respectively.
  1. run the following Visual Basic program snippet. What are the results? (A) 1 (B) 0 (C) True (D) False

Console.WriteLine (1.1 + 1.2 = 2.3)

  1. run the following Visual Basic program snippet. What are the results? (A) 1 (B) 0 (C) True (D) False

Console.WriteLine (0. 3-0. 2 = 0. 1)

what result do you expect? What is the error message actually seen?

because it is a comparison, so I hope there can be a quick way to calculate by hand! Thank you!

Nov.23,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b2b1ff-2ba9a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b2b1ff-2ba9a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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