Ray's New Intellectual Arithmetic · Lesson LIV · Unit 6: Money, weights and measures

54. Business problems with whole numbers

Goal: Your child solves everyday buying, selling and sharing problems.

⏱ About 20 minutes · 5 steps

Open it at the Internet Archive ↗

You'll need

  • The book page (press “📖 Book page”, or use a printed copy)
  • Paper for jotting, though the work is meant to be done in the head

What's in the book

Seventeen problems such as a shopper's wrong change and three men sharing the gain on a horse.

The lesson, step by step

  1. Warm up

    Ask three or four problems from the last lesson again, out of order. Your child answers and says why.

  2. Show the reasoning

    SayThree men paid $90 for a horse and $18 to keep it: $108 in all. They had its use, worth $42, and sold it for $99: $141 in all. They gained $33, which is $11 each.

    List what went out and what came in, then compare.

  3. Work the problems aloud

    Read each problem on the page aloud. Your child answers, then explains in a full sentence, the way the book's model solutions do. The problems go like this:

    Having $92, I bought a watch for $73: how much had I left?

    George bought candles 25 cents, soap 10, sugar 35 and starch 3, paid $1 and got 30 cents change: what was the mistake?

    Three men bought a horse for $90, kept it 6 weeks at $3 a week, had its use worth $42 and sold it for $99: what did each make?

  4. Ask “Why?”

    After each answer ask “Why?” or “How do you know?” Ray's wants the reasoning said aloud, not just the number. If your child stalls, go back to the model and say the first half of the explanation together.

  5. Wrap up

    Pick the two problems that were hardest today. Tomorrow, start with those as the warm-up.

Afterwards

Do the rest of the lesson's problems over the next day or two, a few at a time. Move on when your child can explain them without help.

Answers to the book's problems

1) 165 gal. 2) $50. 3) $185. 4) $19. 5) $35. 6) 3 cents too much change. 7) $2. 8) $12.50. 10) $2.82. 12) 600 yd. 13) 28 mi. 14) 40 lb. 15) $11 each. 17) 100 bu.

Worked out for this site from the scan. If a number in your copy differs, trust the book. Every answer is in Ray's own Key ↗.

@teddyrookbook GitHub