- A6 ; 1,506
- B106 ; 3,090
- C6 ; 1,590
- D60 ; 2,400
Step-by-Step Solution
106 splits as 100 + 6, so the blank is 6. Then 15×100+15×6=1,500+90=1,590. Writing 1,506 comes from gluing 1,500 and 6 together instead of adding 1,500 and 90, and 3,090 comes from leaving 106 in the blank so that the first 100 is counted twice.
Answer: C) 6 ; 1,590
Key idea: From counting to whole numbers
Natural numbers (1, 2, 3, …) answer 'how many?' when there is at least one of something. But what if there are none? You need a number for that — and that number is zero. Adding 0 to the natural numbers gives the whole numbers: 0, 1, 2, 3, …. Every whole number sits at a fixed point on the number line, and they never run out — for any whole number you pick, there is always a larger one.