This question tests ISEE Lower Level Mathematics: finding the missing number in an arithmetic sequence. An arithmetic sequence is a list of numbers with a constant difference between consecutive numbers, and understanding this requires identifying the pattern and applying it to find missing terms. In this specific sequence, [30, 25, _, 15, 10], the difference is -5, meaning each number decreases by 5. The correct answer, 20, fits the pattern because 25 - 5 = 20, and 20 - 5 = 15, continuing the descending sequence correctly. A common distractor, such as 22, might seem correct if students miscalculate the difference or don't maintain consistency. To teach this skill, practice skip counting backwards by 5s, use visual aids like number lines to show the regular intervals, and remind students to verify their pattern works for all consecutive pairs in the sequence.

This question tests ISEE Lower Level Mathematics: finding the missing number in an arithmetic sequence. An arithmetic sequence is a list of numbers with a constant difference between consecutive numbers, and understanding this requires identifying the pattern and applying it to find missing terms. In this specific sequence, [20, 16, _, 8, 4], the difference is -4, meaning each number decreases by 4. The correct answer, 12, fits the pattern because 16 - 4 = 12, and 12 - 4 = 8, maintaining the consistent decrease. A common distractor, such as 14, might seem correct if students mistakenly calculate the difference as -2 or make an arithmetic error. To teach this skill, help students recognize that sequences can decrease as well as increase, practice finding differences in descending sequences, and emphasize the importance of checking that the pattern works for all given terms in the sequence.

The correct answer is 55. To find the rule of the sequence, subtract any term from the one that follows it. For example, 37 - 28 = 9. The rule is to add 9. The missing number is the fourth term, which is 46 + 9 = 55. To check, add 9 to 55: 55 + 9 = 64, which is the fifth term.

The correct answer is $26.00. The question asks for the amount saved in the fourth week, not the total saved. The sequence represents the amount saved each week. Week 1: $15.50. Week 2: $15.50 + $3.50 = $19.00. Week 3: $19.00 + $3.50 = $22.50. Week 4: $22.50 + $3.50 = $26.00.

The correct answer is 17. By observing the given numbers, we can find the pattern. The difference between 9 and 5 is 4. The difference between 13 and 9 is 4. The difference between 25 and 21 is 4. The rule is to add 4 to the previous term. The missing number is 13 + 4 = 17. To check, 17 + 4 = 21.

The correct answer is 63. The rule for the sequence is to subtract 7 each time (105 - 7 = 98). The terms are: 1st=105, 2nd=98, 3rd=91, 4th=84, 5th=77, 6th=70, 7th=63.

The correct answer is 56. The pattern is an arithmetic sequence. The common difference is 26 - 20 = 6 minutes. The sequence of practice times is: Mon=20, Tue=26, Wed=32, Thu=38, Fri=44, Sat=50, Sun=56.

The correct answer is 24. The difference between the fourth term (44) and the first term (14) is 30. This difference occurs over 3 steps (from term 1 to term 4). The common difference is 30 ÷ 3 = 10. The second term is the first term plus the common difference: 14 + 10 = 24.

This question tests ISEE Lower Level Mathematics: finding the missing number in an arithmetic sequence. An arithmetic sequence is a list of numbers with a constant difference between consecutive numbers, and understanding this requires identifying the pattern and applying it to find missing terms. In this specific sequence, [4, 9, _, 19, 24], the difference is 5, meaning each number increases by 5. The correct answer, 14, fits the pattern because 9 + 5 = 14, and 14 + 5 = 19, maintaining the consistent increase throughout. A common distractor, such as 15, might seem correct if students look at the middle position without calculating the actual pattern. To teach this skill, have students find differences between all given consecutive pairs first, practice adding 5 mentally, and always double-check by ensuring the pattern works both forward and backward from the missing number.

The correct answer is 30 grams. The crystal's mass increased by 42 - 18 = 24 grams over 4 days (from Day 2 to Day 6). The daily growth is 24 grams ÷ 4 days = 6 grams per day. The mass on Day 3 would be 18 + 6 = 24 grams. The mass on Day 4 would be 24 + 6 = 30 grams.