Shadowing Arthur Benjamin

Summary

Arthur Benjamin turns mental arithmetic into a live performance, inviting audience members with calculators to check his answers. He begins with squaring numbers, then adds a missing-digit challenge and calculations of the day of the week for birth dates. For his finale, he squares a five-digit number while explaining his thinking aloud. The performance combines rapid calculation, audience interaction and a glimpse of the memory techniques behind the results.

Key points, in order

1. Benjamin first races calculators on two-digit squares, then works through progressively larger numbers. Volunteers verify the answers, making the increasing difficulty part of the demonstration.
2. In another challenge, volunteers multiply a selected number by numbers of their own choosing. After hearing all but one digit of each result, he identifies the omitted digit.
3. He asks for birth dates and supplies their weekdays, checking less familiar dates with a book of calendars. The segment extends the performance beyond multiplication.
4. For the final square, he separates the number into thousands and a remainder, combining their squares with twice their product. He explains that a phonetic code lets him hold intermediate numbers as words and retrieve them during the calculation.

Five useful phrases to practise

Choose a caption line to open Repeat mode. Listen, then say it after the speaker.

1. 1:47 There is something called the square of a number, which most of you know is taking a number and multiplying it by itself.
2. 3:07 Let me try to take this one step further.
3. 8:02 By any chance, does anybody here happen to know the day of the week that they were born on?
4. 12:08 I'm going to break the problem down into three parts.
5. 12:56 I store them as words, and later on retrieve them as numbers.

Based on the video’s captions. Original video: Lightning calculation and other "mathemagic" | Arthur Benjamin · TED.

Everyday phrases from this video

• good morning
• that's right
• first of all
• over there
• go ahead

• Level: B1–B2
• Accent: American
• Length: 15 min · 266 lines to practise
• Speed: about 155 words a minute (an average pace)
• Words: about 2,310; the talk asks 64 questions
• Timing: Sada measures how far behind the speaker you are on every line

What to focus on in this talk

Choose one calculation and repeat the numbers accurately before increasing playback speed.

What this talk trains

Arthur Benjamin speaks for about 15 minutes: roughly 2,310 words in 266 caption lines. The pace eases off as the talk goes on, from about 171 words a minute in the first quarter to 134 in the last. Overall it is faster than 30 of the other 66 talks on Sada. Its sentences average 8.5 words, no longer than the middle of the library (14.3), and 14.5% of its words fall outside the 3,000 most common English words (library middle: 12.9%). It asks 64 questions, so there is plenty of question intonation to copy. Phrases that fast speech often shortens come up again and again: “going to” (9 times) and “let me” (7 times).

Lines from across the talk, and what each one trains

One line from each quarter of the talk. Press a line to open it in Sada, ready to record. “Linking” marks words that run together: a word ending in a consonant sound joins the vowel that starts the next one.

1. 1:33 Would you like to try a more standard calculator, just in case?

   “would you”: fast speech often shortens it to “wouldja”. Listen for whether the speaker does here. A question: listen to where the voice rises or falls at the end, and copy it.

2. 4:55 9,758, this will take me a little bit of time, so bear with me.

   Several commas: say it in short chunks first, then as one line. A number (9,758): practise saying it at the speaker’s speed.

3. 9:21 It goes as far back into the past as 1800, because you never know.

   Linking: say “goes as”, “back into”, “past as” without a break between the words. A number (1800): practise saying it at the speaker’s speed.

4. 13:01 I don't want you to think you're seeing something out of "Rain Man."

   “out of”: fast speech often shortens it to “outta”. Listen for whether the speaker does here. Linking: say “something out”, “out of” without a break between the words.

Words that keep coming up

Words outside the 3,000 most common English words that Arthur Benjamin uses more than once. The number is how often each is said. Look up any you don’t know, then press it to practise the line where it first comes up.

• digit ×39
• audience ×26
• calculator ×18
• fission ×6
• cookie ×5
• calculation ×4
• raise ×3
• applause ×3

How the pace changes through the talk

The fastest minute starts at 1:37 (about 209 words a minute): practise that minute once the rest feels easy. The slowest starts at 11:49 (about 97): a good minute to warm up with.

Measured from the caption timing, so the numbers are close, not exact.

How the talk opens: press any line to practise it

1. 0:12 Good morning, ladies and gentlemen.
2. 0:14 My name is Art Benjamin, and I am a "mathemagician."
3. 0:18 What that means is, I combine my loves of math and magic to do something I call "mathemagics."
4. 0:24 But before I get started, I have a quick question for the audience.
5. 0:27 By any chance, did anyone happen to bring with them this morning a calculator?
6. 0:33 Seriously, if you have a calculator with you, raise your hand.

How to practise this talk

1. Warm up on the slowest minute (from 11:49) or on the opening lines above.
2. Then take the chosen lines above one at a time: a shortened phrase, a question, a line said in chunks, a number, linked words.
3. On each line, press Record and say it after Arthur Benjamin (Repeat) or along with them (Shadow), then open Compare and go again until every word is green.
4. Save the fastest minute (from 1:37, about 209 words a minute) for last.
5. At one minute a day you finish the whole talk in about 15 days, and Sada shows your first try against your latest.

More talks to practise

• Jill Bolte Taylor — My Stroke of Insight (B1–B2 · 149 words a minute · same level)
• Robert Waldinger — The Secret to a Happy Life — Lessons from 8 Decades of Research (B1–B2 · 148 words a minute · same level)
• Steve Jobs — Stanford Commencement Address (2005) (B2 · 154 words a minute · same accent)
• Matt Cutts — Try Something New for 30 Days (B1 · 159 words a minute · same accent)

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