Question

determinati abcd barat daca ab si cd barat sunt invers proportionale cu 1surpa 5 si 1 supra 7; iar ab +cd barat =36

Answer 1

ab; cd ip cu 1/5 ; 1/7

ab * 1/5 = cd * 1/7 =k

ab/5=cd/7=k

ab=5k
cd=7k

ab+cd=36
5k+7k=36
12k=36
k=3

ab=5*3=15
cd=7*3=21

abcd=1521

Answer 2

$\dfrac{\overline{ab}}{5}=\dfrac{\overline{cd}}{7}=\dfrac{\overline{ab}+\overline{cd}}{5+7}=\dfrac{36}{12}=3\Rightarrow \overline{ab}=15;\ \overline{cd}=21;\ \overline{abcd}=1521.$