Description Level D Learning Goals Building on the addition skills up to +4 learned in Level C, this level focuses on training addition from +5 to +10 and addition with larger numbers, aiming to strengthen the essential mental arithmetic skills needed for calculation. Book (Volume/Month) — Issue (Week) — Learning Content Book D1, Weeks 1~4 Addition +5: (1~9)+5, (1~14)+5, (1~19)+5 Addition +6: (1~9)+6, (1~13)+6, (1~19)+6 Achievement Test Book D2, Weeks 1~4 Addition +7: (1~9)+7, (1~19)+7, (1~23)+7 Addition +8: (1~9)+8, (1~19)+8, (1~22)+8 Achievement Test Book D3, Weeks 1~4 Addition +9: (1~9)+9, (1~15)+9, (1~21)+9 Addition +10: (1~9)+10, (1~15)+10, (1~20)+10 Achievement Test Book D4, Weeks 1~4 Comprehensive Addition +5~+10: Numbers up to 19 +(5~6), Numbers up to 19 +(7~8) Numbers up to 19 +(9~10), Numbers up to 19 +(5~10) Addition with Larger Numbers Achievement Test Book D5, Weeks 1~4 Addition with Larger Numbers: Sums of two numbers up to 15 Sums of two numbers up to 20 Sums of two numbers up to 25 Sums of two numbers up to 30 Sums of two numbers up to 35 Sums of two numbers up to 40 Comprehensive Addition (Level D) Final Test