### Brain Teasers

# Lest Outta Tera

Lester owns a factory adept at making a substance called Lest. It is made by using a substance called Tera.

Making 1 unit of Lest involves using 11 grams of Tera and during it's processing 2 grams of Tera are given out which are reusable.

Now Lester has ordered for 128 grams of Tera.

How many units of Lest can be made out of that?

Making 1 unit of Lest involves using 11 grams of Tera and during it's processing 2 grams of Tera are given out which are reusable.

Now Lester has ordered for 128 grams of Tera.

How many units of Lest can be made out of that?

### Hint

The 2 grams of Tera can be reused with another 9 grams to make a unit of Lest.### Answer

Lester can make 14 units of Lest.128 grams of Tera gives 11 units of Lest and 22 grams of Tera are given out with 7 grams already left from 128 thus leading to 29 grams.

These 29 grams can make 2 units of Lest and 11 grams are left out ( 7 left behind and 4 given out during processing).

These 11 grams are used to make 1 unit of Lest.

Thus the number of units of Lest = 11+2+1=14.

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## Comments

Good attempt but a bit too easy. Your answer actually makes things more confusing. Why not simply note that each unit of lest requires a net of 9 units of tera. 128/9 = 14 with 2 remaining.

You can't just divide by the net amount, stm8. You luck out and get the right answer in this case (although really you didn't, because you said there were two left over, which there aren't). In this case, if you started with 127 units, you would only be able to make 13 units, where your method would still give an answer of 14 units.

stm8r1 is on the right track. The last gram of Lest

made requires 11 grams of Tera at the start, although you

get 2 back. Every previous gram of Lest only requires 9 net

grams of Tera. So subtract 2 from the initial grams of Tera,

and divide the result by 9, dropping the remainder, to get

the amount of Lest produced. The amount of Tera left over

is the remainder of the division, plus the two grams produced

by the final process. In this case, there are indeed two grams total

left over, produced by the final step.

made requires 11 grams of Tera at the start, although you

get 2 back. Every previous gram of Lest only requires 9 net

grams of Tera. So subtract 2 from the initial grams of Tera,

and divide the result by 9, dropping the remainder, to get

the amount of Lest produced. The amount of Tera left over

is the remainder of the division, plus the two grams produced

by the final process. In this case, there are indeed two grams total

left over, produced by the final step.

Whoops, you're right, dewtell. My apologies to stm8r1 on that note, but the method still wouldn't work. Again, if there were 127 units at the start you would have only 10 units at the end to make the 14th Lest unit. Even though the net is 9 Tera's per Lest, you still need 11 to make the last unit.

Right. So if you started with 127 units

and subtract 2 as I suggest, you get 125.

125 divided by 9 is 13 remainder 8. So

13 Lest grams would be produced, and you would

have 8+2 = 10 grams of Tera left over at

the end.

and subtract 2 as I suggest, you get 125.

125 divided by 9 is 13 remainder 8. So

13 Lest grams would be produced, and you would

have 8+2 = 10 grams of Tera left over at

the end.

Yeah - dewtell, we're both saying the same thing. I was just too numb to realize what you were saying in your first comment.

stm8 is quite right in this case. This is a bit like the frog in the well teaser. It would have been more teasing if the order was for 126. Then 126/9=14 but you have to back up once in the process (like the frog who doesn't slide back after he reaches the top). After 13 processes there is 13x9 = 117 Tera used. If we start with 126 that leaves 9 remaining. Not enough to make one more process. In this case you borrow 2 Tera from the Terabanker, run the process one more time and repay the loan with the extra 2 produced. Oh silly me! What sort of a Terabanker wouldn't want interest on their loan?

I did (128-2)/9 = 14, which is what people before said, but using a lot more words.

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