Questions

Charles Macintosh (29 December 1766 – 25 July 1843) was a Scottish chemist and inventor of waterproof fabrics.He devoted all his spare time to science, particularly chemistry, and before he was twenty resigned his clerkship to take up the manufacture of chemicals. In this he was highly successful, inventing various new processes. His experiments with one of the by-products of tar, naphtha, led to his invention of waterproof fabrics.

An up - selling is getting the customer to spend more money, buy a more expensive model of the same type of product, or add features or warranties that relate to the product viewed or purchased. 

A cross - sell is to get the customer to spend more money by adding more products from other categories than the product being viewed or purchased. 

1) ability to support multiple processors
2) virtual storage
3) source level debugging

Yes, you are requested to write an essay as part of your TOEFL iBT exam. There are 5 major types for TOEFL essay topics. They are:

1. Agree or Disagree

2. Preference

3. Description / Explanation

4. If / Imaginary

5. Compare & Contrast

The best way to prepare for this essay writing is to understand the writing style clearly. To understand the the genre, you can refer some sample essays submitted before by different contestants. You can get such sample TOEFL essays from various sources such as TOEFL training websites, cheap essay writing service sites, online libraries, etc. Once you are well aware of the writing pattern the next thing is to practice writing random essays. Keep in mind that you should practice writing essays of all above mentioned 5 types. If you make it a routine to write random essays, gradually you can compete at higher level to write the given essay topic for your TOEFL iBT exam.

Let the two digits be x & y

From given data in the question, we get

x + y = 3(x - y)

x + y = 3x - 3y

=> 2x = 4y

x/y = 2/1

For having the 2:1, numbers satisfying are

12, 21, 24, 42, 36, 63, 48, 84

From this 36 is eleminated because it is a perfect square and no others are prime or perfect squares.

Hence, there exists 7 such 2-digit numbers => 12, 21, 24, 42, 63, 48, 84.