what is 15ft by 25ft in squared metres?

1 ft = 0.3048 m

Area
= (15 × 0.3048 m) × (25 × 0.3048 m)
= 34.84 m² (to 4 sig. fig.)

1 ft = 0.3048m exactly by definition of a foot.

I like converting each measurement as I go, saves me confusion:
15ft (0.3048m/ft) x 25ft (0.3048m/ft)
= 34.83864 m² exactly <<< exact answer.

Now let's round off to 2 digits since 15ft and 25 ft both have just 2 digits:
35 m² <<< better answer.

===

Convert feet to meters by multiplying by 0.3048 (meters per foot):
15' ≈ 4.6m
25' ≈ 7.6m

Multiply those two dimensions together:
4.6m x 7.6m ≈ 35 m²

Answer:
About 35 sq. meters

34.83864

First we need to find the square footage found by multiplying the length by width.
15ft^2*25ft^2= 375ft^2
Now we need to convert from square feet to square meters
m^2 = (ft^2)/10.746
m^2 = (375ft^2)/10.746
(375ft^2)/10.746 = 34.9m^2 (approximately)

You can also do this by changing the feet to meters then multiplying
m= ft/3.2808
15ft/3.2808 = 4.57m
25ft/3.2808 = 7.62m
4.57m*7.62m = 34.84m^2 (approximately)

Converting from feet to meters then multiplying the length and width is more accurate than finding the square footage and converting from there so the best answer would be ~ 34.84m^2
(~ means approximately)

http://www.metric-conversions.org/area/square-feet-to-square-meters.htm
http://www.metric-conversions.org/length/feet-to-meters.htm

15*25/(3.28084^2) m^2