The question you opened
The soil in a six foot hole
A hole in a field is 6 feet deep and 3 feet across.
How much soil is inside the hole?
None of it
A hole is the space where soil used to be. The dimensions describe the emptiness, and emptiness holds nothing.
A hole is 6 feet deep and 3 feet across. How much soil is in it. None. A hole is defined by the absence of the material around it. Digging one removes soil. What remains where the soil was is empty space, and the question asks how much soil is inside that empty space. The numbers exist to start your hands moving before your reading catches up.
Given a depth and a width, multiplication feels inevitable, and it produces a real quantity: the volume of the hole. That volume is the soil that came out, sitting somewhere else now, in a pile or a truck. Even the multiplication is a small trap of its own. Three feet across is a diameter, so a cylindrical hole holds pi times the radius squared times the depth, which is pi times 1.5 squared times 6, roughly 42 cubic feet.
Treating it as a 3 by 3 by 6 box gives 54. The choice offered in the question is the box answer, and it would be wrong even if the question had been about the hole. The useful habit is to name what you are measuring before you measure it. Say the noun out loud: soil, hole, water, air. Then check that the numbers you were given describe that noun. Depth and width describe the hole.
Nothing in the question describes soil at all. The same slip happens in less playful settings. A survey reports the number of people who answered, when the interesting number is the people who did not. A cost estimate covers the work, when the question was about the disruption. A dashboard shows sessions when the question was about people. Dimensions describe shapes. Shapes are not always the thing you were asked about. One second spent naming the noun catches this, and it costs nothing.
Technique: Ask what is being measured