Description Level D Learning Goals Building on the addition skills up to +4 learned in Level C, this level focuses on addition from +5 to +10 and addition involving larger numbers, helping children develop the mental math skills essential for strong calculation ability. Book (Volume/Month) - 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 to +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 of Larger Numbers Achievement Test Book D5, Weeks 1–4 - Addition of Larger Numbers - Addition where the sum of two numbers is 15 or less - Addition where the sum of two numbers is 20 or less - Addition where the sum of two numbers is 25 or less - Addition where the sum of two numbers is 30 or less - Addition where the sum of two numbers is 35 or less - Addition where the sum of two numbers is 40 or less - Comprehensive Addition Review (Level D) Final Test