A satellite is composed of 30 modular units, each of which

[RonPurewal]

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[steve.tan.chee.wei]

i was lost with the wording and try to solve this using smart numbers.

since it's mentioned that in one unit there's 1/5 of non upgraded sensors to the total upgraded sensors of the satellite.

thus i pick

non upgraded sensors per unit : 20
total upgraded sensors per satellite: 100
and since all unit has the same amount of non upgraded sensors: 30 * 20 = 600

thus fraction would be: 100 / (600 + 100) = 1/7

[RonPurewal]

i was lost with the wording and try to solve this using smart numbers.

since it's mentioned that in one unit there's 1/5 of non upgraded sensors to the total upgraded sensors of the satellite.

thus i pick

non upgraded sensors per unit : 20
total upgraded sensors per satellite: 100
and since all unit has the same amount of non upgraded sensors: 30 * 20 = 600

thus fraction would be: 100 / (600 + 100) = 1/7

This approach is flawless. Do you have a question about it?

I agree with your (implicit) contention that the words "upgraded" and "non-upgraded" create confusion"”and that this confusion is the primary source of difficulty/pure annoyance in this problem.
So, when I look at this problem, I just think
"upgraded" "”> red
"non-upgraded" "”> blue
For me at least, it's much easier to think about red sensors and blue sensors than about "upgraded sensors" and "non-upgraded sensors".
Perhaps that will help.

(If you are actually trying to ask about something else altogether, please clarify. Thanks.)