Question

от бревна отпилили сначала 30%,а потом от бревна отпилили сначала 30%,а потом 40% остатка.после этого длина оставшейся части бревна стала 2,1 м.сколько метров отпилили от бревна во второй раз?

Answer 1

Всего - ? - 100%В первый раз - ? - 30% от всегоВо второй раз - ? - 40% остОсталось - 2,1м - 60% ост 1) 100% - 40% = 60% - осталось2) 2,1/ 60 *40 = 1,4(м)  Ответ: 1,4 м отпили от бревна во второй раз. 

Answer 2

Problem Analysis

The problem describes a scenario where a log was initially cut by 30%, and then the remaining log was cut by 40% of the remaining length. The resulting length of the log after these two cuts is 2.1 meters. We need to determine the length of the log that was cut the second time.

Solution

Let's denote the original length of the log as L. After the first cut, 30% of the log is removed, leaving 70% of the log. After the second cut, 40% of the remaining log is removed, leaving 60% of the remaining log, which is equal to 2.1 meters.

Calculation

We can set up the equation to solve for the original length of the log: - 60% of L = 2.1 meters

Let's solve for L: - L = 2.1 / 0.6 - L = 3.5 meters

Answer

The original length of the log was 3.5 meters. Therefore, the length of the log cut the second time was: - 30% of 3.5 meters = 1.05 meters.