“ REFLECTION 2 ”

By : Elsa Winda Prastiana

09313244015

At previous meeting, Mr. Marsigit showed some video about mathematics education. Among other things about Word Problems. In video 1, we can learn how to solve word problems use an acronym BUCK$ to solve word problems. BUCK$  is Box the question, Underline the info needed, Circle the vocabulary, Knock out un-needed info. We use the BUCK$ system to simplify, organize and solve the problem. Academic Vocabulary very important to solve word problems. Then in Video 2, also explained again about to solve word problems in mathematic. In this case, some of basic things to think about where training how to solve the word problem is to figure out what is the fact and what is being else for.   

From video 3, we learn how to solve puzzles and riddles otherwise known as word problems using two variables. An example the problem is a first number plus twice a second number is 23. Twice the first number plus the second number is 31. Find the number. Then we solve this, suppose the first number is x and the second number is y. From the information, we can get the equation x + 2y = 23 and the second equation is 2x + y = 31. From equation 1 we get x = 23 – 2y. Then, we substitute the value of x in the second equation. We get 2(23-2y) + y =31. Then, we calculate 46 – 4y + y = 31. After that we get -3y = -15. So, the value of y = 5. Then we find the value of x is 13. Finally, we get the first number is 13 and the second number is 5.

In video 4, we learn about properties of log. Properties of logarithms is :

a.      log_b x=y ↔ b^y=x.

b.  log_10 x=log x ;log_e x= ln x

c.  log_b (M ∙N)= log_b M + log_b N

d.  log_b M/N= log_b M - log_b N

e.  log_b x^n= n log_b x

      From the properties above, we can solve this problem : 

1.   log_10 100=x. The value of x is 10^x=100. So, x = 2.

2.  log_2 x=3. The value of x is 2^3=x. So, x =8.

3.  log_7 (1/49)=x  ↔ 7^x=1/49
                               ↔ 7^x= 1/7^2
                               ↔ 7^(x)= 7^(-2)
                               ↔ x= -2