Maths is not needed now, we have calculators. A speech against calculators.
Answers
Step-by-step explanation:
In general, the point of learning *any* skill is so that you will be able to do it when it might be helpful to you.
Calculators are readily available (especially now that cell phones are ubiquitous) but given the option between doing something on the calculator vs doing it in your head (provided you have that skill, of course), doing it on the calculator is not always the best choice. [But certainly sometimes it is.]
For routine calculations with everyday numbers, just doing it in your head is almost always much faster than taking out your phone, loading up the app, and typing in the appropriate numbers. Also, much like how you look uneducated if you can't properly read standard text in the company of others, you also look similarly uneducated if you can't do basic math in your head in the company of others. [In other words, “Why learn to read on your own when you can just type it in your phone (or even just take a picture of the text) and have the program read it to you with text-to-speech?” Can you imagine how cumbersome life would be? Before literacy was as widespread as it is now, many illiterate people sincerely believed that they were perfectly fine not knowing how to read and that learning to read wouldn't really help them in their life. Because they didn't know how to read, they did things that didn't require literacy (obviously), and as such they couldn't even appreciate all the ways literacy *could* improve their lives if only they were able to read decently.]
Another important downside to calculators is that they are very precise and accurate-on-their-own-terms, but they don't always give the answer to the actual problem you have. They give the precise and accurate answer to the string of symbols you punched in, but that is not always the string of symbols you *meant* to punch in, not the string of symbols you *should* have punched in. It is easy to hit the wrong key (even moreso on a touch screen), or miss a key, or double a key. It is very, very easy on a calculator to get the calculator's *syntax* wrong, and punch in the terms in the wrong order for what you want the calculator to do and so get from the calculator the right answer to a question you didn't want the answer to. These types of errors are very rare in mental math.
Mental math has the very real benefit that you *know* what you are working with and what steps are being taken to get to the result. Estimation is frequently an early step in the mental calculation, which means you make sure that your answer ends up in the right ballpark even if it's not exactly right at the end (whereas on a calculator it's a common problem that people get an answer that is off by orders of magnitude and don't even notice that they are way, way off).
Calculators have their place, but that is really as a support to mental math: speeding up parts of calculations (with mental estimation as a checking mechanism) that take a long time to do by hand but which aren't actually the point of the problem in question. They are also great for double-checking math you've done by hand / in your head.
There are other reasons for learning to do math without a calculator, but those are some anyway.
Step-by-step explanation:
In general, the point of learning *any* skill is so that you will be able to do it when it might be helpful to you.
Calculators are readily available (especially now that cell phones are ubiquitous) but given the option between doing something on the calculator vs doing it in your head (provided you have that skill, of course), doing it on the calculator is not always the best choice. [But certainly sometimes it is.]
For routine calculations with everyday numbers, just doing it in your head is almost always much faster than taking out your phone, loading up the app, and typing in the appropriate numbers. Also, much like how you look uneducated if you can't properly read standard text in the company of others, you also look similarly uneducated if you can't do basic math in your head in the company of others. [In other words, “Why learn to read on your own when you can just type it in your phone (or even just take a picture of the text) and have the program read it to you with text-to-speech?” Can you imagine how cumbersome life would be? Before literacy was as widespread as it is now, many illiterate people sincerely believed that they were perfectly fine not knowing how to read and that learning to read wouldn't really help them in their life. Because they didn't know how to read, they did things that didn't require literacy (obviously), and as such they couldn't even appreciate all the ways literacy *could* improve their lives if only they were able to read decently.]
Another important downside to calculators is that they are very precise and accurate-on-their-own-terms, but they don't always give the answer to the actual problem you have. They give the precise and accurate answer to the string of symbols you punched in, but that is not always the string of symbols you *meant* to punch in, not the string of symbols you *should* have punched in. It is easy to hit the wrong key (even moreso on a touch screen), or miss a key, or double a key. It is very, very easy on a calculator to get the calculator's *syntax* wrong, and punch in the terms in the wrong order for what you want the calculator to do and so get from the calculator the right answer to a question you didn't want the answer to. These types of errors are very rare in mental math.
Mental math has the very real benefit that you *know* what you are working with and what steps are being taken to get to the result. Estimation is frequently an early step in the mental calculation, which means you make sure that your answer ends up in the right ballpark even if it's not exactly right at the end (whereas on a calculator it's a common problem that people get an answer that is off by orders of magnitude and don't even notice that they are way, way off).
Calculators have their place, but that is really as a support to mental math: speeding up parts of calculations (with mental estimation as a checking mechanism) that take a long time to do by hand but which aren't actually the point of the problem in question. They are also great for double-checking math you've done by hand / in your head.
There are other reasons for learning to do math without a calculator, but those are some anyway.