Помогите сделать домашку

1.
|3.9-4|=|-0.1|=0.1

2.
0.385-0.001≤n≤0.385+0.001
0.384≤n≤0.386
Ответ: 1)

3.
734.256≈734.3

4.
$\frac{| \frac{1}{7} -0.14|}{|0.14|}*100 = \frac{| \frac{1}{7} - \frac{7}{50} |}{0.14}*100= \frac{| \frac{50-49}{350} |}{ \frac{7}{50} }*100= \frac{1}{350}* \frac{50}{7}*100=$
$= \frac{1}{49}*100= \frac{100}{49}= 2.04$
2.04%

5.
P=2(61+12.4)=2*73.4=146.8≈147
S=61*12.4=756.4≈756