If the projector in your classroom is fairly new, it might have a HDMI port on it. In this case, you can use a standard HDMI to HDMI cable to easily connect your laptop to the projector.
For older projectors that only support VGA, you will need to buy a VGA to HDMI cable or adapter to connect your laptop.
Yes you can use the HDMI cable to connect your laptop to a projector provided your projector is a new one and supports it. Otherwise you have to use VGA adapter only.
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