Pick a Number
If typing a single word into Google gets you too many documents, you can narrow your search by typing in more words. For instance, searching for needle sewing finds only documents that contain both the words needle and sewing—about 145,000 documents. Searching for needle sewing embroidery finds only documents that contain all three words—about 37,000 documents.
Sophisticated users target their hunts by performing advanced searches, which use terms and symbols such as minus signs, the word OR, and quotation marks. To omit a word, precede it with a minus sign. For example, searching for puzzle –crossword finds documents that contain puzzle but not crossword. To search for words that appear either separately or together in a document, use OR. Searching for cause OR effect returns documents that contain only cause or only effect, or both cause and effect. To specify an exact word order, use quotation marks. Searching for black hole finds more than 2 million documents that contain both words, not necessarily together, while searching for “black hole” finds only the scant 1 million documents that contain both words together and in order.
For puzzle purposes, let’s suppose we have 10 documents, each containing only a single word—the name of one of the numerals 1 to 10. We will use a Google search to pick out some of these documents by looking for particular letters. For instance, if we searched for e i, we would find the three documents five, eight, and nine—in other words, those documents that contain both the letters e and i. (Note: We’ve taken a few liberties in describing how Google works. In reality, Google will find an individual letter only if you precede it with a plus sign.)
1. [Easy] How many documents are found by the search t OR f?
2. [Easy] Which single document is not found by one of the following four searches: h OR w, f r, i –g, “en”?
3. [Medium] Find only the first five documents—one, two, three, four, and five—by replacing the question marks in ? OR ? OR ? with the right letters. For instance, searching for g OR h OR w would find the documents two, three, and eight.
4. [Hard] Find only the odd-numbered documents—one, three, five, seven, and nine—by replacing the question marks in “??” OR ? –?. For instance, searching for “fo” OR i –e finds the documents four and six.