Born on 4/22/2010
Whether or not they could have figured out the relative weights of these objects, consider for a moment the life of a 5 year old in the 21st century: Phones are cordless and wireless and small enough to fit in your pocket. Not having worked in an office you have likely never seen a phone with one of those funny squiggly cords (except maybe at Grandma's house).
Computers are tiny and are more likely to be laptops or tablets or wireless phones than PCjr-era desktop machines with huge CRT monitors. In fact, you've never even seen a CRT monitor. You may have encountered a desktop-type computer but if it was anything other than just a big LCD monitor with a keyboard then it was almost certainly a tower-style design and not a wide flat blob on the desktop.
Speaking of desktops, paper planners are an unknown concept as well.
This whole question appears to have been designed in 1960 and carried forward unchanged ever since. And you people think the biggest problem facing our schools is the cutback of a few teachers.
"Rarely is the question asked, are, is our children learning?"