From a timber 13 m long, first sawed off a few meters, and then another 1/4 of the remaining part.

From a timber 13 m long, first sawed off a few meters, and then another 1/4 of the remaining part. How many meters did you saw off the first time if you sawed off 7 meters in just two times?

Let X meters be cut from the timber for the first time.

Then, for the second time, they sawed off from the bar.

(13 – X) x (1/4).

Then, according to the condition: X + (13 – X) x (1/4) = 7.

X + 13/4 – X / 4 = 7.

Let us bring the left-hand side of the equality to a common denominator.

(4 x X + 13 – X) / 4 = 7.

(3 x X + 13) / 4 = 7.

3 x X + 13 = 28.

3 x X = 15.

X = 5 meters.

Verification:

5 + (13 – 5) x (1/4) = 7. Correct.

Answer: The first time sawed off 5 meters.