Question

b159a kumon
addition and subtraction of 2-digit numbers

1. fill in the missing numbers in the number sequences.

(1) 22 -1-> 21 -1-> 20 -1-> -1->
(2) 18 -2-> 16 -2-> 14 -2-> -2->
(3) 34 -2-> 32 -2-> 30 -2-> -2->
(4) 47 -2-> 45 -2-> 43 -2-> -2->
(5) 54 -3-> 51 -3-> 48 -3-> -3->
(6) 61 -3-> 58 -3-> 55 -3-> -3->

Explanation:

Solve subtraction problems on page B158b

Calculate the differences and missing values for questions (9) through (16):

• (9) \(85 - 34 = 51\)
• (10) \(85 - 42 = 43\)
• (11) \(86 - 63 = 23\)
• (12) \(87 - 75 = 12\)
• (13) \(85 - \Box\Box = 34 \implies 85 - 34 = 51\)
• (14) \(85 - \Box\Box = 42 \implies 85 - 42 = 43\)
• (15) \(86 - \Box\Box = 63 \implies 86 - 63 = 23\)
• (16) \(87 - \Box\Box = 75 \implies 87 - 75 = 12\)

Solve number sequences on page B159a

Find the missing numbers by applying the indicated subtraction rule for each sequence:

• (1) Rule: \(-1\). Sequence: \(22, 21, 20, \mathbf{19}, \mathbf{18}\)
• (2) Rule: \(-2\). Sequence: \(18, 16, 14, \mathbf{12}, \mathbf{10}\)
• (3) Rule: \(-2\). Sequence: \(34, 32, 30, \mathbf{28}, \mathbf{26}\)
• (4) Rule: \(-2\). Sequence: \(47, 45, 43, \mathbf{41}, \mathbf{39}\)
• (5) Rule: \(-3\). Sequence: \(54, 51, 48, \mathbf{45}, \mathbf{42}\)
• (6) Rule: \(-3\). Sequence: \(61, 58, 55, \mathbf{52}, \mathbf{49}\)

Answer:

Page B158b: Subtraction Problems

No.	Problem	Answer
(10)	\(85 - 42\)	\(43\)
(11)	\(86 - 63\)	\(23\)
(12)	\(87 - 75\)	\(12\)
(13)	\(85 - \Box\Box = 34\)	\(\Box\Box = 51\)
(14)	\(85 - \Box\Box = 42\)	\(\Box\Box = 43\)
(15)	\(86 - \Box\Box = 63\)	\(\Box\Box = 23\)
(16)	\(87 - \Box\Box = 75\)	\(\Box\Box = 12\)

Page B159a: Number Sequences

No.	Sequence	Missing Numbers
(2)	\(18 \xrightarrow{-2} 16 \xrightarrow{-2} 14 \xrightarrow{-2} \Box \xrightarrow{-2} \Box\)	\(12, 10\)
(3)	\(34 \xrightarrow{-2} 32 \xrightarrow{-2} 30 \xrightarrow{-2} \Box \xrightarrow{-2} \Box\)	\(28, 26\)
(4)	\(47 \xrightarrow{-2} 45 \xrightarrow{-2} 43 \xrightarrow{-2} \Box \xrightarrow{-2} \Box\)	\(41, 39\)
(5)	\(54 \xrightarrow{-3} 51 \xrightarrow{-3} 48 \xrightarrow{-3} \Box \xrightarrow{-3} \Box\)	\(45, 42\)
(6)	\(61 \xrightarrow{-3} 58 \xrightarrow{-3} 55 \xrightarrow{-3} \Box \xrightarrow{-3} \Box\)	\(52, 49\)