How to use While loop

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Vy Do
Vy Do on 11 Sep 2020
Commented: Vy Do on 12 Sep 2020
I have this problem "Suppose you start multiplying the numbers 1.1, 1.2, 1.3, 1.4,1.5, ... together. Use a while loop to determine how many of these numbers you have to multiply in this way to get a product that is greater than 100000." This is the code I have so far but the answer was wrong. I know that there's something wrong with the line y=y*(y+0.1) but I don't know how to express the multiplication of 1.1*1.2*1.3 and so on. Could you please help me with this?
This is my code
y = 1.1;
c = 0;
while y < 100000
y = y*(y+0.1);
c = c+1;
end

Accepted Answer

Stephen23
Stephen23 on 11 Sep 2020
Edited: Stephen23 on 11 Sep 2020
You need to keep the running total and the current value of y separate, e.g.:
y = 1.1;
t = y;
c = 1;
while t<1e5
c = c+1;
y = y+0.1;
t = t*y;
end
Independent check:
>> V = 1.1:0.1:9;
>> find(cumprod(V)>1e5,1,'first')
ans = 19
  2 Comments
Vy Do
Vy Do on 12 Sep 2020
Thank you. 19 is the right answer. However, my c at the end is 99990 if I use the same code you have. In this case, my professor wants the c will be the value answer so I don't know if we can fix this a little bit so that it will return c=19 for answer?
Vy Do
Vy Do on 12 Sep 2020
Sorry, you're right. I know where my code went wrong, instead of t<1e5 for the while condition, I typed in y. Thart's why it returned c as 99990. Thank you again.

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