AC Lim's answer to liang liang's Primary 6 Maths Data Analysis Singapore question.

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AC Lim
Ac Lim's answer
13116 answers (A Helpful Person)
Let the number of row at 1st = u
Total chairs at 1st = 15u

After removed 6 chairs
Total chairs = 15u - 6

There are u + 9 row of 12 chairs.
Total chairs now
= 12u + 108

Therefore,
15u - 6 = 12u +108
3u = 114
u = 38

So, Total chairs in the end,
= 15u - 6
= 15×38 - 6
= 570 - 6
= 564.

Chairs for briefing = 564