It’s always mind-blowing when a fellow adult reveals they didn’t know something that EVERY GROWN UP PERSON SHOULD KNOW.

It makes you wonder, “wow, how did you get this far in life without knowing that?”

These 25 folks from AskReddit recall the times they experienced this with other “adults” and it made them do a double take. Read on and prepare to be flabbergasted.

1. That’s a tough one

My college roommate asked me how to make a sandwich. Like how to actually put mayonnaise on the bread and slice a tomato. He was 22 and had recently been accepted to medical school.

2. Alarms

I’ve met more than one person who doesn’t get fire alarms. When my husband and I first got an apartment together, we were cooking and we burned something; the smoke caused the smoke alarm to start beeping. Instead of opening the window to let the smoke out, like a normal person, he calmly walked to the door and began putting on his shoes to go outside and wait for the fire department to come – because he thought that when the smoke alarm goes off, that’s what you do. After all, why else would we have gone through all those fire drills in elementary school?

3. Where is that darn thing?

I work in technical support. I regularly deal with customers who have no clue what/where the space bar is.

It has been in the same location as since the mass production of the Remington typewriter, May 1st, 1873.

4. Gas problems

My grandmother is 88 years old. Drives a Ford Mustang.

Does not know how to put gas in her car. Has literally driven cars for 70 years without ever once using a gas pump. She calls me every few weeks to go over there and follow her to the gas station, so I can pump for her.

I don’t have the heart to tell her that the employees will do it if she asks nicely, since it’s one of the few occasions where I see her.

5. The two-hander

Showed a grown man how to use a hammer. He started off trying to use two hands.

6. “I am no longer with this girl”

My girlfriend in college didn’t know how to boil water. I explained how easy it was (water goes into pot, pot goes on stove, turn on the stove) and she did it, then left the pot there for four hours waiting for the water to “finish boiling”. Of course all of the water evaporated, she completely burned the pot, and then started to panic and cry because she didn’t know how to turn the stove off.

I am no longer with this girl.

7. Obsolete keys

Met a woman in a parking garage that didn’t know that her key could unlock the door. She flagged me down to ask if I could give her a ride to get a battery for the button that unlocked the door so she could get into her car.

8. The dreaded steak knife

I dated a guy, he was 19, that did not know how to use a steak knife. Instead of sawing the meat, he attempted to force the knife through it by simply pushing down. I don’t know if you don’t know this, but steak is not quite the same consistency as softened butter. He kept shaking the entire table,we were in a restaurant, as he tried to force the knife into the meat. Eventually I stopped him, took his knife, and showed him how to saw the meat – his mind was completely blown. When I asked him how it was possible that he didn’t know how to do this, he told me “oh, my parents usually just let me pick up the meat in my hands at home.”

We broke up a couple months later.

9. Genius material

How to wash your face.

I think most people dating back to early humans have figured out the cup your hands under running water, lean your head over the sink and bring your hands up to your face process.

I lived with an adult girl who did NOT know to do this. She would just swat the water up at her face and get the sink, the counter, the mirror, the toilet, EVERYTHING soaking wet.

10. Public transit

I’m a senior in college and I still find myself shaking my head when my classmates don’t know how to use the campus bus routes to get back home.

11. Getting close…

A friend of mine tried to cook rice in the kettle because she understood it involved heat and water. That was her logical conclusion… She’s 27.

12. It still ran?

My girlfriend went 15,000 miles without getting an oil change. She thought you only bring it in when there is a problem.

13. This is an educational failure

I’ve recently had to explain to someone in their twenties what sexually transmitted diseases are. This person had no idea.

14. Wasteful

My current roommate has no idea how to shop for groceries/manage the food he has already bought. Now, we live about a 3 minute walk from a pretty large grocery store, so food shopping is by no means inconvenient. His food is constantly rotting in the fridge; when he orders out he leaves the leftovers in the fridge until they have to be thrown away; he currently has 3 half-eaten bags of chips. He probably ends up throwing away $100 worth of food every month.

15. Simple Math

Giving tip! My friends are sweet and DO tip, but figuring out 10% or 20% is like rocket science to them. – Move the decimal over, BOOM. 10%. Need 20%? Double that.

16. I have a feeling this is pretty common…

I was asking my chemistry teacher about something in high school, junior year, a few years back and a girl was behind me with her student notebook out. I knew she probably wanted to go to the bathroom so I told her to go ahead and she gave her notebook to the teacher to sign her a hall pass but he handed it back because it was blank and asked her to write the date and time. She turned around and stared at the analog clock for about 10 seconds and said ‘I can’t tell time’.

17. Blinds

I had an ex-girlfriend that still couldn’t figure out how to open/close blinds. She was 23.

18. Show me!

Roommate once asked where the stamp goes on the letter he was sending.

19. She probably dumped him

I have one friend who is ridiculous with this kind of thing. He’s 28, and the most notable thing I remember is that he was planning to buy a bouquet of tulips for a girl a week before his date, because he thought they didn’t die. His reasoning was that they stay alive all summer in the ground.

20. Boom

My wife, lighting her cigarette in my gas-leaking Jeep after asking why it smells like gas in here.

21. Old Folks

You are 70 years old; I refuse to believe that you do not yet understand the concept of promptly paying for your purchases. That has been the name of the game for over 20 years now.

22. The blender?!?

Had to teach my 20 year old girlfriend how to grate cheese. She said her mom just put it in the blender. It made me sad to think about all of those taco nights without properly grated cheese.

23. Showed him

My 23 year old brother and I bought one of those big jugs of iced tea powder and he asked me, “So, do you just dump the whole thing in and add the water?”. I said yes. Priceless.

24. Techincal terms

My boyfriend cannot understand anything but the exact time in exact numbers. If you say “quarter after 4” he has no idea what you’re talking about. Also, refuses to learn.

25. Ha!

My mom can’t remember whether blue or red is associated with hot or cold. When she’s in the car and wants to turn on the air conditioning, she just randomly sets the dial to one side or the other and waits for the air to come on to see whether she’s right or not.