1 This is the arithmetic problem: 3 * 3 meters = 9 square meters. The effective area of the heart is about 75%.
Then 9 square meters * 75% = about 7 square meters.
Considering that you still need to light up and look beautiful, I suggest that the spacing between candles is 10 cm, which means that each candle covers an area of 0.1* 0.1= 0.01m2.
4 Total area/average floor area = quantity = 7/0.0 1 = 700.
I'll tell you one more thing. The distance of 3 meters by 3 meters is a huge area, and a large living room will almost be occupied with no place.
Another serious problem is that when you light so many candles in a row, the first one may have burned out when you light the last one.
So I suggest you use a meter square and a hundred candles to get it done. If I were you, I would surround a group of red and white roses, decorate 20 lilies in the middle (if it was my 20th birthday), and then put candles, which would be more beautiful.